If its for a group project, I think anything over 1/8" is too much. I've gotten squares in a block swap and trying to put them together, (made my quilters who I would have expected would know 12 1/2" is 12 1/2", not 13")was a PAIN to put together! For myself, I know what I can and can't work in, but not if I have to give it to someone else.