Rubber bands break during the opening sequence, it's a fact of life. but they need to be TIGHT, even double-wrapped if necessary. If this is an F111 Canopy, then it's also probably got Dacon lines (or are they Microline?) Reason I ask is the size of the stow also matters. The 'bite' that a Dacon line should have in a stow is about 2.5 inches, for a Microline stow, 1.5 inches is closer to the mark. I PROMISE you that, with everthing else being equal, good tight line stows will give you a more stable opening sequence.
One of these days I'll use my GoPro when I pack and I'll show you how to fold it to get it into the bag. I can actually get up and walk away from the fully open back with the canopy folded up in it, and it's would come out (betcha can't do that with S folds!)
You really want to get this down right before you start rasslin with Zero P...pack one of those wrong and it will rock your world.