It was designed for a 4 stroke. however I'm in the "its gonna stick out mode" myself. I was going to use an inverted pitts muffler from Slimline, however it won't fit between the motor and firewall.

If you really want to get picky, IMO, the plane was designed around the YS 110. Unless you currently own one or have been on a waiting list for a few months already, you can't get a YS 110.

After flying mine with a OS 160, Horizon may have been right with the "different motor" comment, not sure the Evo 100 will deliver the performance a hard cord 3D pilot will desire.