yeah I saw a video on the net of a tt500 trails bike i dont know what frame it was in but I think it was a mix of ty250's and 175's it looked like it worked ok from what I saw
that 400 250 mix i'm not sure how well it worked because I only saw a few sections where he rode it and it wasnt a pretty sight i'm not sure if it was the bike, rider, or both but the rider was line 4(Beginner line) and i don't think a yz400 motor is the most controllable motor out there but it's still a neat idea