[bodywerks]

You will probably want to cut the exhaust tips so that they only stick out of the fuse by about 1/4-1/2". if you can get them short enough to where they slide straight through the mounts then it's a breeze. With mine on my Extra, I couldn't do this, so I made the forward mount removable. I then slid each pipe through the rear mount first, then slid the forward mount over both pipes and mounted it, like so below.

IMPORTANT!!!!!!! it seems that the clamps alone on the teflon couplers are not always enough to keep the pipe on and the backpressure can blow them right off the header. And because you have to cut the stock headers to a length of about 10 inches (you knew this, right?), you lose the factory extrusion that helps to keep the coupler from sliding off the header as well. To prevent this, many guys are seriously roughing up the pipe and header with radial scuff marks with something like a cutoff wheel or 60 grit sandpaper, then the first engine run is done at no more than a high idle for 5-8 minutes to really warm the coupler up to get it to flow into the grooves and grip the pipe/header better.
Others are drilling and tapping the coupler/pipe and header and tapping it for like an 8-32 or 10-32 screw and putting a screw in them with red loctite.
I actually drilled mine and used countersunk aircraft-grade blind rivets and then put the clamps over the rivet heads.
You could also fashion up some sort of rubber stopper at the back of each pipe, like I did on my H9 260 (also seen below).