Nope, never had any bother, Ive got mine set so the straps are a tight fit, once its on your back its very snug. The only problem is sometimes if it gets full, and your bending over to pick another one up, the top one will drop out and land on the ground The plastic drum holds about 15 and by the time it gets to that weight you know its there
A pic to illustrate what it looks like
very good idea, gona try and sort my self one of them out,