Why don't we let the normal flow of product reviews to take place:
if your users are happy, they'll leave you good reviews; if they don't like it, they'll post a critical review (not just 4/5 reviews).
if you want to make sure it works with RetroPie, then you should test it and advertise as such. It's only you that can provide support for the gamepad/fight stick, not the reviewers or this forum.