Glad to hear you got it back in the air.
I was just looking at the peak temps when I came up with that value not the average.
You will probably have to fuss around with the low and high mixture for a bit as you have changed the compression and it might take a while to find the sweet spot again.
As far as the muffler they can be fun to find one that will work as well in all aspects as you want. But I do like the "look" of a in cowl muffler rather than something that looks like a water heater hanging off the plane.

Just nice to hear you got it in the air and no dead stick...