Hi Alan,
IIRC, we always used the tongue mufflers on the FP 40s. And most of the stock mufflers I saw in use had the stinger cut off and the holw opened up a bit.
If I am in error, don't fret......... Randy will jump on me and set me straight!
Since the OS 40 FP, Fox 35 and several others will share mufflers, the choices are great! Makes balancing a *little* easier.
Btw: Randy's CNC machined tube mufflers are outstanding.........