I have a 7.5 RTR kyosho and got a used sp1 chassis but my 7.5 is 4 mm longer and that seems like its as long as the sp2 did kyosho use a longer chassis for the rtr but just use the old suspension on the rtr I do not have a rtr 2 but mine is like the last batch of the old rtr before they went with the rtr 2.