It's all about what makes the field owners happy. I know a few places out here (Cali) that are 350, though at the same time I have played a CQB field that had a max of 400. To me there is no difference in the pain level, you are still getting shot a lot, very close, but it would be a safety thing. Can your eye protection REALLY handle 6-10 rounds at near point blank?
What are the restrictions on full auto going to be? Also will the lighting be adjustable? (playing games with the lights out in CQB is awesome) The more information the better!