One option could be to let both domains point to the same forum. I agree that owners of the 2021+, red KTM-based bikes hardly will seek information at the GG-specific forums in any case. But there will be new owners of secondhand GG bikes, and those owners may seek info on the net and find (as we all do) lots of knowledge among the loyal fans. It would be strange for them to seek info in a Rieju forum, as they may not be aware of the connection.