Size of Pro Heat panel for T8

[veganpython]

Hi,

I'm making a decision on which Pro Heat panel to order for two T8 cages with shelves. I'll be housing one ball python in each cage. I have gotten recommendations from Pro Heat on 2 different sizes - 75 watt i.e., 12" by 18" (if room temp is mid 60s and up) or 100 watt i.e., 12" by 24" (if room temp goes below 65). For those of you who have T8, can you take a minute to tell me:
1) what wattage/size you got
2) your room temp in summer and winter,
3) the challenges you have, and
4) if you were to do it again, would you pick the same size or would you size up or down and why

Thank you very much for your feedback!