I have the Vetterman exhaust for the IO-540 and am very please how well it fits together. I have temporarily installed the header pipes onto the engine as well as both mufflers.
Vetterman sells some "hangers" to secure the muffler/tail pipe assembly which consist of steel rods and rubber hose for vibration purposes. The instructions from Vetterman stated to secure the hangers vertically between the muffler/tail pipe and engine mounts but in my configuration I do not have a center engine mount available.
A quick search of the Bearhawk forums showed folks with the 540 engine were using one vertical hanger to either the engine mount or to a bolt on the engine sump case, with a second hanger placed horizontally between both muffler/tail pipes. The folks who attached the hanger directly to the engine sump case feel the muffler/tail pipe should not be isolated from the engine due to vibrations, especially at startup. However, on the flip side, folks who are flying with the vertical hangers attached to the engine mount have not experienced any problems or vibrations.
I see merit with both schools of thought and think that in my case it will come down to which method works best with my installation. And that is yet to be determined.
