I can't comment on the cowl fit on the Cap but I can comment on the performance in the 15 pound range. I run a Brisson 2.4 in my MW Extra and love the performance. I run a 19x8 Mejzlik and have unlimited vertical. The engine is silky smooth, I have never tried a larger prop but do read I may be on the small side of prop spectrum for this engine. I would not expect spirited 3D performance but if scale is what your after you should really like the combo

Vince L