FKY1000,

Wow, that's some serious looking muffler. I think a Pitts muffler will not fit inside the cowl either, as there's not much room below the engine inside the cowl. This cowl really is only good for inverted mounted 4-strokes, and perhaps a side-mounted small-case 4-stroke like YS 63.

I have a TT 61 Pro sitting around, and my Funtana 40 is also sitting around w/o flight pack. I haven't bothered to tailor the F40 for the TT61 yet.