Steve,

I am using the Tower Hobbies .46 muffler on my .46FX.

With an 11.5x6 prop, RPM has improved by about 600 RPM, over the de-baffled original OS 873 muffler. I am told that when using 10x6 and 10x7 props, the improvement is about 1,200 RPM over the original OS 873 muffler, with the baffle in place.

If you buy the Tower Hobbies .46 muffler, you will pay $15 and if you buy the Hobbico muffler, which is essentially the same thing, you will pay $13.

The Nelson SuperThrust is an efficient tuned silencer, but it shouldn't be any more expensive than the Tower unit.

It must be made of gold...