Man sound complex zab. I've been thinkin on this as well, buy I think it would work better the other way.

This is what I mean. So, 4% is deducted for promos. Deduct another 4% as insurance against that person only. So, it builds until it reaches 2k or 3k for each member and that is held by you against that member defrauding another member. U can stop after that amount or keep collecting and repay it to each member at the end of each week. It's like a bonus, for being a good member of the community, and insurance against those that would want to defraud the community.