I have a 90SP in a H9 Hellcat. I cutout between the top two dummy cylinders in the dummy radial face. Then built two scoops in the inside of the cowl to redirect down across the engine. Then two big cutouts in the bottom rear to exit. The dimesions are roughly the 1 sq inch in and two out as recommended. Yet it still overheated and quit on the first flight.

I could tweak the inlets and stuff more but I have seen references in forums about big radial engine planes not being an issue like the tightly cowled ones (Spits and Mustangs). I haven't found any details as to why that's the case. Now I really don't care that much about a truly scale appearance and so I'm wondering if just removing the dummy engine (or a portion of) would solve the problem.