The head sticks out one inch.

Unfortunately I don't have more close up pictures of the muffler installation.

I did have to cut the notch out of the firewall, and make the tank compartment cover. I didn't find it too difficult, just a bit of ply as a sort of frame, and 1/32 inch ply to form the channel. There is enough space to put in a 10 ounce dubro tank. The tank center ends up aligned properly with the carb.

The extension is 1/2 inch. 3/4 would make things a bit less tight. The extension has the added benefit of lowering the tuning rpm of the exhuast a bit - which I view as more suitable for this type of plane. (The Jett is tuned at 15000 rpm)

Note, it is *not* tilted at a 45 degree angle. It is something less than 45. I just placed the engine over the firewall and estimated the position so that I could get the blind nuts in place before gluing the firewall to the fuse. Use a compass to draw a circle centered on the indicated engine center, and passing though the indicated (i.e. the punches on the die cut peice) blind nut holes. The location of the blind nuts for the rotated mount should fall on that circle to ensure the center does not move - if that makes any sense.