Your never going to stop the Low-Life Rob-and-Duplicate. There's always going to be someone(s) who are going to say they did it 6 months before you. Really sucks
Either the Low-Life or a Low-Life's loyal lap dog will get a hold of the product and reverse engineer your hard work developments and call it their own. That has been going on for-ever. Can't stop it unless you patent it which isn't going to happen because of the costs.
All you can do is draw up a contract waiver threaten to sue and make lots of noise on the internet about personal shit that has nothing to do with it grind off all the bolts and weld the transmission together at every seam making it so it will have to be disassembled with a sledge hammer hopefully destroying all the improvements made so R&D is impossible.
Atleast if any thing make it more difficult!