I built a large deck out of Trex about 7 years ago. The best thing I have ever done. No splinters, no maintenance, no cupping, etc. etc. I live in the Midatlantic area so heat only gets up to 95 degrees at most. So I can't comment on the effects of exteme heat. I built the deck with std 16" on ctr studs and the 5/4" decking was at 45 degree angle. I have had no problem with sagging. The deck has a nice soft feel to it because of the small flex. Several contractor friends have commented that the deck would still be there in 100 years. I believe them. Final word....just do it. Trex is a great product.