I'm not going to high horse this. I STILL haven't painted the body on my xr5. I just run it naked like an uncultured ape because I'm just so paranoid about borking the paintjob and I keep hemhawing around about paying someone with skill, talent and ability to do it.
My old X4 rally I didn't cut window vents. I was only runnin a 26cc in it and I never really had heat issues. It was a pain to start it and then put the body on though.
At minimum i'd cut out a few pockets in the side windows and the rear window to keep it from wanting to catch air.