None of the experienced members around will go ahead and „risk“ their funds - even if it’s not a lot - in order to do this. You may reconsider, choose trusted members and send them the „bounty“ upfront so they can test and review. That’s just my two cents though.
This has happened before, and I can assure that no experienced member will risk their
BTC to try out the platform, If OP indeed needs honest reviews from reputable users, he would have to send them the rewards first or at least make use of an escrow.