Might I ask - why does this need adjusting in this way?
I don't know. It just looks that way. Trial & error decision.
My patch uses renovation_percentage in somewhat different way then before => new 'best' value must be found.
Also, I have just applied the patch: when I try to generate a new map, I get a runtime error relating to an uninitialised variable "f" at line 4345 of simcity.cc - what is "f" for?
Yes. it wil break 'city avoid high place' behaviour.
It was cut&paste error in my commit 3bae1da8f2eaa26a1d9400a73ed9878b437c1c27.
Fix pushed to github.