I have a Wren MW54 Mk II (12 lbs. thrust) in my '16. Due to the fact that the Wren is a bit longer than the P-60, I had to mount the tailpipe with no gap between the tailcone of the engine and the bell-mouth of the pipe. I couldn't get the engine any further forward without hacking up the inlet duct. I was amazed at how quiet this setup was. On the test flight, it sounded like it was only at half power on takeoff. In the air it was a pooch! I was somewhat disappointed. I contacted Wren and explained the particulars and they suggested that I move the pipe back a minimum of 10 mm... about 3/8". I did this and I just let the pipe hang out the end of the airplane. Now it is about twice as noisy on takeoff and it performs much better in the air. These tests were done on very similar days...same temp, humidity and Baro.

I hope that this helps,

John