hahahahahaha.I just cut mine right after the muffler and said screw the turndowns. Sounds AMAZING!!
why you laughing? :dunno it does sound amazing. I have mac's by the way toohahahahahaha.
i would leave like... 2-3 inches.. so you have room to slide the turn down on.
if your going to clamp it..
if you plan on welding it.. 1.5-2 inches.. so you can slide it on and weld it.
hope that helps