Adding insulation WITHOUT tearing up the rig??

BEWARE of Reflectix inside windows in the sun on hot days. It can heat up the windows enough to melt the sealant! I caught mine early enough it only got tacky, but a quick search found plenty of folks who got theirs so hot the sealant ran out. If you can shade the window from the outside, then it works great! Just not when the window gets direct sun all day.

Also some sort of shade on the roof will help, as will slide toppers, since slideouts have much less roof insulation.