ORIGINAL: plugin
How can I know if Ill be needing to replace the stock muffler on a O.S 75AX to fit it in the cowl of a Great Planes Extra 300 (60)? I could sure use the $40 of the pitts muffler for something else...
First the Pitts style mufflers work very well with the 75 AX. No problems what-so-ever.
As to how you "know"... that's basically up to you.
A Pitts style muffler will give the plane a better "look" and may require far less cowl cutting, which is a good thing, but you could also probably install the stock muffler, at worst using an extension.
Much like with ANY ARF, you have to play with the fit to make it work.
If you've never done this before, you may want to enlist the aid of a more experienced builder to help you out, as cowls are easy to ruin.