I also feel like upper and lower temps should have more effect on each other
I agree, personally.
Ultimately I want to make it so that the temps actually impact the other slightly (upper being way overheated when the lower is quite cool, causes a slight increase in lower temp and a slight decrease in upper temp) --- since the change I made to damage already results in "damage if one temp is particularly high, OR both are fairly high".
That is the next thing I plan on messing around with, after I've finished my current playthrough with the changes I've already made - since knowing the equations used right now, I suspect the math on that will require a good bit of tweaking as well.
edit: Though, DAB, you wouldn't mind outlining what changes achieved those effects, would you?
Uhh... how familiar are you with scripting?
If the answer is somewhere in the vicinity of "not at all", then my outlining changes probably won't be that useful.
If the answer is closer to "pretty good / proficient", then the best approach would really be to crack open the PPAMain script and follow it through to learn what it is doing and how it is doing it... then reread my description of what I did and go from there (and/or ask pointed questions if something in particular isn't making sense to you).
My changes are almost entirely dealing with script modifications - and Imp's scripts are complex enough that in my opinion, it isn't advisable to play around with them unless you're able to wrap your brain around the whole thing first.
(PS. "DU" would be my requested short hand... DarkUncle is the real handle -- but it was already registered when I came here, so DarkUncleBoh became my backup -- since Dark Uncle is the nickname for a literary character whose real last name is Boh... but I digress over trivial matters)