RE: Convoluted speed theory
Everything bob27s says makes sense. Since I need to make a new cowl for my AT-6 anyway, I'll give the mostly-closed-front concept a try, making the inlet area in front of the engine 50-75% of the outlet area. I still like my idea with the firewall treatment, so I won't change that. I'll patch up my old cowl well enough to try for comparison too, and it might be interesting to try a spinner vs. the spinner nut I have been using. Those are easy things to swap around and try at the field. WaveOsScope will tell all!