Well it is time to go back to the drawing board. The ring exhaust I wanted to use does not fit and it looks like the modification necessary to make it fit is not going to be easy. I want to thank Free Bird for posting his photos; they helped me to see something I missed. When taking measurements for clearance on the ring I forgot to take into account the wooden cowl brace attached to the fuselage and the glow plug driver caps. If you look close at Free Bird’s second photo in the first group, you can see there is not much space for the exhaust, wood ring and glow plug wire housing.

I am going to mount the engine again without the exhaust and take measurements again with the plywood ring and glow driver installed. BTW, the reason I asked for the exhaust exit at the 9 o’clock position is to match the aircraft in the photo. As you can also see from the full scale example, there is a gap between the fuselage and the cowl, which could solve the clearance issue. I’ll update after I decide how I will move forward.

I included photos of both the standard Keleo ring and the custom so you can see the difference in clearance between cylinder head and exhaust.