RE: Convoluted speed theory
I guess my thinking up to now was that exit area = cooling. With a larger front opening, you have a positive pressure situation vs. ambient inside the cowl, so no more air enters the cowl than is exiting, or in other words the excess oncoming air would just spill around the outside of the cowl anyway, just as it would with the front of the cowl mostly closed. I do see the point of guiding the air around with the cowl fron mostly closed though, vs. leaving it to chance what path the air takes.
Vic, when we inspect engines, the cowl must be removed completely, so there is no need to increase access to the carby with a bigger hole in the cowl.