I mod 372 mufflers from time to time. Here’s one I put a few thanks through. 3/4” pipe and a second little outlet. Didn’t realize the little outlet would do some melting when I added it
Can I suggest you would be better fitting the exit on the recoil side similar to the other stub in position & angle then no hot exhaust gases being directed onto the log being cut & getting possible fire with a long WOT cut