Is there any way to limit the size of generated strings? I see the :max-size stuff in the context of checking properties, but I want it for generating samples.

You can control size for individual generators

See gen/scale

Is there anything that would cause thread contention? I'm trying to generate samples of collections in parallel, behaving oddly.

Hmmm, maybe it was just the scale thing.

I can't think of any threading pitfalls