Dick,
The inlets on that picture are very small, similar to the small size used by the German speed nuts. The majority of pictures I have run into show an inlet much smaller then the fined area. Even some of the 1920 radial planes had a modest size inlet. As far as outlets they have gone all the way around a radial engine, on the bottom of the cowl of a full size Cessna or on top of the wing on many speed models. It seems if you are looking for low pressure you would find it on top of the wing.
Thanks for your reply