I always go small on tubes. For example, I just put, IIRC "23-28" tubes in my 32mm tire. They're much easier to install w/o bunching up and I really have no fear about undue stretching. First, I've never had the problem and second, when you think of it, anything that comes through the tire itself is going to puncture your tube whether it's full thickness or a little thinner.
I use the same rationale for buying lightweight tubes instead of regular for my go-fast bike. Actually a cheap way to save quite a bit of wheel weight with no consequences (again, in my years of experience).