i have the 80watt RBI radiant heat panel that i installed myself on my sole PVC enclosure. i try to DIY stuff myself if i can. anyway my PVC enclosure is from fellow forumer AKA Dave of Scaley Enclosures (i believe in supporting my friends) and it's about the same dimensions of a T8.

the wattage or size of the heat panel should not matter as long as u have it regulated by a thermostat IMO. i would only buy and ship my heat panel to AP (or other PVC enxlosure makers) if it is not already assembled. they can install it for u which basically means screw it to the top of the enclosure.

if u have your enclosure at home and it's assembled (and sealed), just do it yourself. (or call me over and i'll do it lol) the key to installing it is not using screws longer than the thickness of your PVC.