RE: 30cc Edge 540 build
As far as using the stock muffler goes it does fit in the cowl. It leaves about 1/4" clearance from muffler to cowl, but you have to trim nore of the underneath of the cowl off to allow muffler tip to clear and vent outside cowl. Using the jtec pitts style you pretty much just have to trim for cylinder head to clear. As far as function goes stock muffler will work fine but it will not look as clean when finished using jtec or similar pitts style wrap around muffler. I will be ordering a Jtec for it eventually no rush to get her in the air as the Cleveland weather makes flying no fun.