I don't have direct experience with that muffler on that engine. But I have a lot of experience with pitts style mufflers on small STs (90 on down) and have found them to be very tolerant of pitts style mufflers. I never noticed any power loss but I never took comparative rpm readings either.
I would go ahead and use it. I don't think you'll have any problem. But don't be expecting a big power boost. Be happy if you stay even.

Denis