ON that same D-7 I made a huge muffler. It is like the one that are sold for Ryobi conversions but much longer.

The body is aluminum gas cylinder stock. I turned the outside to about 1/2 the original thickness. It is light but, on this airplane weight is not a problem. The end plates are aluminum flat stock disks that have a shoulder so they press fit in the cylinder. The front plate bolts to the engine. The aluminum spacer was needed to clear the cooling fins. A piece of all thread is used to keep the ends secure. The pipe is an old piece of camping chair or tent pole. The is nothing fancy inside. Just huge volume, which seems to be key. This airplane is unusual in that is has a perfect place to put such a huge can.

I may make some dummy engine parts to secure with hose clamps. If there are any signs of the bolts securing it to the manifold being stressed I'll secure the tail end. I think some thing simmilar could be made of a hair spray can or simmilar.