Thanks for the input everyone. After reading the comments, I was feeling pretty confident that a 32 spoke wheel would suit my needs, and then I found the same hub in 36. That may be overkill for a small wheel, but there's a chance this hub could end up on my full-sized touring bike, where I definitely want 36 spokes, so I'm happy to have the option. I already have some 36 hole 20" rims kicking around, so all that's left is to find a source for really short spokes. Or have them cut.