It's actually not a stupid question. I'm not finished my Giant U-Can-Do yet, but I mounted the my O.S. 160 with the standard muffler last week. My engine and muffler came with an adapter. The adapter bolts on at the engine exhaust flange then the muffler bolts on to the adapter, all from the muffler side. I will remove the cowl tomorrow and send some better photos of the engine, adapter, and muffler. I did however have to cut one of my Allen wrenches down to clear between the adapter and muffler.

Cheers

George