I'm assembling a Sportsman Aviation Waco .60 and will put an O.S. 90 four stroke in it. I would like to install a pitts muffler but would like to see some detailed 3-views, so I know what I'm dealing with before I order one. I've been to the SlimLine site, but there doesn't seem to be any detailed specs that I can see. Am I making too big a deal out of it? Should I stop sweating it and just order one? What do you all do/suggest?

Will the engine be mounted inverted or sideway?

Inverted.

Just make sure you have around 2" of clearance between the cylinder head and the firewall since the muffler canister will be sitting in that space. I believe the diameter of the muffler canister is around 1", but there are two muffler pipes coming out of the canister that angle slightly back.

Thanks Richard, I appreciate the help.

I just measured the diameter of the muffler canister, and it turned out to be 1-1/8". In anycase, you should be fine if you have at least 2" of clearance between the firewall and the cylinder head. You might need to trim a little off the bottom of the firewall for the two muffler pipes to clear.

I'll have to do some measuring tonight. Haven't even eyeballed it yet, but I think there's a strong possibility that with the rear mounted carb on the four stroke, plus the room needed for the muffler, might put the engine to far forward for the engine mount. We'll see. Thanks again.