I like to to add a breathing tube to my 4 cycle powered airplanes except I use a brass strap to clamp it the muffler with the outlet dumping into the exhaust path to blow it clear of the aircraft. I got the idea from a retired gentleman at one of the local fields. He had them on all his airplanes and they were simple to build. The strap was formed around a steel drill bit so the brass tub was under the strap as well as soldiered to it. A screw and nut clamped it around the muffler.