Reality is the YZ250 frame was all new in 2005 and was a massive development program. Can't recall details but there was loads of variations of frames tested with lots of diffferent flex characteristics etc. The likelihood of bolting on a frame designed for a much heavier engine with totally different power delivery and achieving an improvement is probably slim to none. If they could produce a generic frame or even use common radiator shrouds I would think it would lower manufacturing costs and be worth while for them. The reality is that the latest model already uses the latest technology finely tuned to the latest 2 stroke engine they produce. The fourstroke frame is no more advanced. On the flip side this is just such a cool project, like yourself I'd build one just for the fun off it. Go for it, it will be different, I bet still handle as good as most people can ride and super super cool. Well Done Dude.