Scott,

The firewall mounting area is about 4 in. tall by 4.5 in. wide. I don't have my ST2300 mounted yet, so I can't give you a picture. If you check the GSP site, you will see the engine box sits high on the front of the plane. I checked and I was right, the 2300 w/ stock muffler will completely fit inside the cowl when mounted at 90 deg. Very nice paint job on the cowl, by the way.

Good luck.

I almost forgot to add that the wingtips have 4 deg. of washout in them. That should help with tip stalling but I guess I'll find out for sure when I get it in the air.