RE: SIG MUSTANG 450 pylon racer
I built one back in the early 80's completely stock. It was awesome! Be real careful on the CG placement. It is quite a handful if the CG is even a little off to the rear.
I had an OS .40FSR in mine (not a racing engine) and it was a fun sport plane that was still fast enough for me.
Don
PS: I have another one NIB...have to get to it one of these days.