... lent my kite once and got it back with a tear 3 inch long on the leading edge. I hadn't noticed til I was about to launch the kite and I could see the bladder!! I threw a patch of the sticky back cloth on and a year later its still going. I'd been meaning to get it done properly but its still going good.
I figured a good key to successful repairs with sticky back is that its nice and dry before you stick the stuff on the kite. Same as richswing, I used some glue around the edges when ever I do Leading edge repairs.
Mind you, big holes is another story and when repairing old kites seems be hard to get the sticky back cloth to stay on even after washed in fresh water and dried well!
cheers,
Robbie