I just got the YS 120SR Heli engine to put into a older Align 700. The muffler for this thing is very expensive like $250 but one for a YS.90RS is only $100 and it's a Hatori #939 Is there any difference. The 90 is the same mounting pattern. Some would say the engine would run hot because the one for the 120sr is bigger and other people say there the same - just use the cheaper one. Maybe there's a expert that has tried both. Also is the 120sr a good fit for the Align 700 - older model