I personally have never seen a shock body damaged from a crash. Its normally the tower and shock ends that give.
I went from 13mm shock on my mbx5r to jammin 16mm shocks. I noticed that my car felt more stable later into 20 minute mains. It didn't seem to bottom out as easy, and was more predicable. Here it is easily 100 at 9pm, so the heat is an issue. With the 13mm i was running the 1.4 pistons with 650 oil, but with the 16mm, i can run the 1.4 with 450 and keep a more consistent feel.
You should temp your shocks after a 20 minute main to see how hot they are. Compare it to a temp before you start running.