Lots of responses this time. I hope it can be forgiven to post a second chapter within 24 hours and reply while I'm at it.

@hApo, I was wondering when this question would come, and a bit hoping for it (it should bring out some interesting talks).
I basically have two reasons and one that is not so legitimate for using such short trains (which are about the maximum a C11 can pull without slowing down on the basic track).
The first is the monthly cost. Costs per car per block go slightly down with more powerful locomotives. Discarding the Ceres and other locomotives that are too slow for my taste, the C11 can pull three cars for 1.53, while the 2-5-1 can pull 7 cars for 2.75, or 0.51 per car for the C11 versus 0.39 per car for the 2-5-1. The 2-3-0 is probably much better, I haven't tested it, but given it's power it should be able to pull 12 cars for 2.94, or 0.24 per car. But 12 cars, a locomotive and a tender take 7 blocks of platform. At 72 per block per month, that's a monthly cost of 504. After some experimenting with early trains, I found that this offset the gains the 2-5-1 made. So I took up a basic philosophy of making short trains and lots of them. This may not be the best way though, and I welcome others to point out their reasons for longer trains.
The second reason is quite simple. As you can see, I cast some eyes on the 2-3-0 later on in the game. But it and it's tender cost a combined 65,000 excluding the cars, which at this stage of the game (with a seasonal income of some 40,000) I simply do not have. I already had to temporarily retreat from expanding the rail network at all in the previous chapter. So my policy is that I prefer a smaller train that I can afford today over a much larger one that I have to save for and can buy several seasons later (I don't want to go into debt).
Eventually, this basic strategy will prove untenable the same as the buses. I'm aware that eventually I invite overcrowding of the lines. That will be the signal to consolidate into more powerful trains, and upgrade the tracks (I'm a bit surprised no one has started about that yet).
The not so legitimate reason is that I like to 'spread out' delivery at the industries a bit. With one big train all the goods arrive in one big delivery, and then nothing for a long time. I hope four trains bring cargo every quarter of that period or so. It's not so legitimate because with double track and even passing tracks, I find the trains pile up behind each other, though at the busy lines around Sandnes the many different kinds of traffic keep the trains separated.
@Matthi, the refinery crowding (which is pretty bad, at one point there were over 400t plastic in the factory on top of the overcrowding in the station) was the result of neglecting to take out the goods for too long in chapter 9, due to being distracted by the passengers traffic while trying to save for a second train. My freight stations by the way are constantly crowded, which is more or less intentional neglect. Warehouses and infrastructure cost me money, which is still at a premium. Taking away the goods would be a good idea, but I can't buy vehicles fast enough (yet) at this stage without going into debt. And also I'm worried of merely moving the problem further down the line, with eventually the stockpiles of the Shopping Mall running over. I'm still a long way from that, but I'd like to approach that slowly. By the way, do factories start to produce faster if they have more stockpiles?
@Severous: The yellow signal is a pre-signal, of which the technical term would be an entrance signal (the real pre-signals tell a train to slow down because the main signal shows a red light and the train needs a kilometer or more to come to a full stop). Pre-signals in Simutrans are connected with the next signals (in this case the station platforms). If the platform for the train is not clear, the train will stop at the pre-signal instead of in front of the other platform, allowing the other train to leave and preventing jams.
The goods train is hauling a load of plastic to the goods factory. On the way back it will pick up what goods are available and drop them off at Sandnes station, where the line passes through. I'm not sure, but I think you gave that suggestion yourself to one of the other forum members.
Regarding the possibility of getting to the end before the end of this week, that will be a negative. I'm at early 1938 now with the game, and that took me three weeks to get there. Thank you though for promising to update the summary. I've noticed that my way of dealing with the situation is somewhat different from most people and raises some eyebrows

, so it will be nice to compare if the results are much better or worse. So far it seems to be more or less comparable.
Anyway, time for another chapter.
Chapter 10: Q2 - Q4 1935, the wood madness.
Total Population: July: 16,430
Total Population: October: 16,713
Total Population: January 1936: 17,389
1935 Population Growth: 1,867
Net Wealth: July: 1,183,908
Net Wealth: October: 1,235,303
Net Wealth: January 1936: 1,313,413
Operational Profit Q2: 71,126
Operational Profit Q3: 73,036
Operational Profit Q4: 93,709
Operational Profit 1935: 313,040.53
Travels Q2: 36,010
Travels Q3: 36,300
Travels Q4: 38,860
Travels 1935: 146,742
Apparently Haugesund has a large number of Russian immigrants, as it builds a Russian church.
In April, the wood line becomes ready. In this case, trucks bring the planks to a station opposite the plantation, where a train brings it further to the factory. The trucks then go empty to the plantation and pick up a load of woods for the sawmill, where they pick up planks again.
Not surprisingly, this new line quickly turns out to be the highest capacity of all. In just two months, three trains are running.
Meanwhile, the normal expansion and vehicle replacement programs continue. Stavanger gets it's Russian church in August.
With Stavanger and Haugesund now both topping 3,500 souls, it is clear to company management that a rail link between the two cities has a rightful place on the priority list. However, analysis* have shown that the investment in the necessary high-speed infrastructure and rolling stock currently goes beyond Rogatrans' means. Therefore, management continues to pursue quick wins in order to get the profit increase needed to fund this future project.
* Read: Experiments. It turns out that a rail line RogaTrans can afford earns 10,000 less than the buses do. I suppose higher speed trains can redress that balance, but I don't have half a million in ready funds to buy tracks and especially multiple runner-pulled trains. So right now I keep giving the highest priority to transporting more freight, which boosts the monthly income.

The situation around the tree plantation. The zigzag in the rail line is for a future rail line to Stavanger, that can go straight ahead. The empty space in between is reserved for the second track, which connects in a straight line to the passengers platform at Haugesund station.

Haugesund Station after the planks line was completed. There's one through track in the middle that doesn't have a platform, in the long run this is supposed to become the Sandnes-Stavanger passengers platform. In Dutch stations it is fairly common to have three tracks between two tracks.
The empty steel train in the middle is on a waiting track, for which it has a special waypoint order. Other trains pass on the outside track to it's right, but as the steel trains have a 100% load order, if one train is loading and another arrives, the entire station would grind to a halt. In the waiting track, up to two steel trains can wait without hindering the rest of the traffic.