Here is some more from ckret. it's some what money related, so I'll post it here.
"Cooper made an inspection of the chutes when Tina was present. As well as the money and the bag the money came in. He made his concerns clear to Tina about the money bag. He checked the money and made statements about that. He stated several times, "no funny stuff," providing nonfunctioning equipment would be funy stuff. Reason dictates that if he new the reserve was a dummy he would have said something about that as well.
I doubt that Cooper would have been able to gain any information about the wind conditions by throwing a chute off the air stairs. It was dark, the chute would have instantly disappeared from his sight the moment he let go of it.
Of course almost anything is possible, but the evidence points to him jumping with it, not that he did, it just points in that direction."