I've never heard of someone saving a wing in a crash by using nylon bolts. I use them because they don't vibrate loose, but I once nicked a tree with a Cessna that had nylon wing bolts and when I picked plane up off the ground the bolts were still tight to the fuselage mount... minus the fuselage!

But on the rubber band topic, it's really not a big deal. It may take 20 seconds longer to put rubber bands on than it does to secure 2 wing bolts. You can invest the 2-3 hours to do a conversion on a lot better things in this hobby, but fly the trainer as designed and look forward to screwing in the bolts on the sport plane you'll soon graduate to.