Cyberwolf, I will definitely post some results. This could prove to be a real bargain hop-up.

FBD, the prop in the photos is a Zinger Pro 12x8. I'll also try a Zinger Pro 12x6 and an APC 11x10 (I don't have a 12x7 or 11x9). Other props I can try are APC 11x8, 11x11, 12x6 and 12x8. I agree that being a long stroke it should do well with the bigger props.

I have both an ABC and a ringed version of the SF. I just had a new ring installed and the top of the liner honed by Frank Bowman.

Here's a photo comparing the sizes of the SK and Tower mufflers. The SK is smaller in diameter, but about 3/4" longer.

David