Even if I threw money at making it a fast 250 - are there still parts out there? If a fast 250 is merely one that has been matched, flowed, ported and really well setup - then what is to stop the same being applied to a 300? (well, I guess the main consideration is the less than ideal bore/stroke ratio of the 300).
I spent years racing a fast RS125 filled to the brim with stuff and that really did take two years of careful setup, recording and diligent use of the weather station (2 stroke racers best friend!) and also tuned a RG50 bucket from nothing to... well... something less than nothing. Can't the PGM-IV curves even be dealt with to some degree by selecting the optimum curve and then fooling the gearbox sensor?