Well, I haven't found anything else that matches the muffler screw spacing for the NV .40 engine yet. So that means you would have to make a bridge adapter for the engine to fit a different muffler. Another thought is to contact the Bisson muffler folks to see if they'll make you one. They may do it as the NV engines glow and the gas engine have been around a while now. If I remember right, J'Tec also can make custom mufflers too. Another thought is to locate one of the old style Tatone manifolds. Tatone made several types including ones that let you decide which hole to open up for the exhaust outlet.

The NV engine is really light weight compared to other .40 engines so it works good in those planes that don't need extra weight up front. I have one in a Hotknife 3D profile stunt plane and it worked out really well in it. Lots of power and plenty of power to hover and still pull out of a hover too. It has a 6 ounce fuel tank and I don't think i have used more that 3 to 4 ounces of fuel for the flights.