I don't have the amps in yet (still working on wiring) but heat should not be a problem. The top doesn’t go all the way up the speaker enclosure under the rear window, so air will flow to the trunk area where the subs are going.
As far as weight, its 1/2" MDF and weighs 10 lbs with mounting hardwear. Its the price you pay, although I toyed with the idea of making everything removable, but the wiring is the biggest problem. I thought of using military vehicle/helicopter type connecters/disconnect but its too much of a pain.