Hi — happy to test this for the 14 days if you still need testers. I'll admit I also built a small app for this exact problem (PeerPlay, reciprocal testing exchange) — mentioning it not as a pitch but because it might save you from manually tracking everyone's opt-in status. If you'd rather just coordinate directly here that's fine too, just drop the link.
https://play.google.com/store/apps/details?id=com.testerhub.app