Kevin,
The Hatori muffler-header combo makes the YS 1.10 sound real good, seems to have added
a little power too. The mount you have sounds just like the one I'm using. The only modification
I did was to make a small releif in the wing belly pan and enlarge the bottom opening in the cowl
to clear the muffler, pretty easy. The down pointed stinger keeps the airplane clean too.

Good luck with your installation
tommy s

PS: GM1
I used the stock pull-pull wires, control horns, etc and have been flying pattern competition with
it for over a year and have had no problems and lately I have been practicing the advanced pattern
with the positive and negative snaps and still no problems.