The stock muffler is about 1/2" shy of making the mark. It would require either an extension or a gaping hole in the side of the fuselage and FIREWALL...neither would be desired.

BTW...I contacted Horizon Customer Support and described my situation...

They suggested I use a different engine...This comes directly form Horizon!

I also called Brisson to see if they made an inverted Pitts style muffler for the Evolution 100 and they said that Horizon never contacted them about a new engine hence they haven't manufactured a muffler for it.

Wouldn't you think that KNOWING your customers were going to require a different muffler solution for an engine that YOU recommend for a model you distribute...You might actually contact the after market muffler manufacturers and let them know there might be a demand for a new product.

HORIZON and HANGAR-9 YOU HAVE SOOOOO MISSED THE MARK ON THIS ONE!!!

(and your customer service leaves something to be desired...)