If a vest is flapping on your shoulder then it's too big. Correct cuts and sizing combinations can make it hard to find exactly what works best but it can be done. You haven't found the perfect fitting vest yet. If you want to make that one work then make it work. If you think cutting holes in it for vents will help then do it. Otherwise it will just end up being a piece of gear you own but hardly ever wear and a good fitting vest can be worth it's weight in gold....which really isn't much but you get my point.