I installed a forward feed sump configuration using an Air Flow Performance
injection system For the 360.  The inlet is very high above the crossover
exhaust pipe and the opening is right underneath the spinner. This required
a contour extension of the lower cowl line and the opening is about 1/2 inch
behind the prop.  I also assymetrically extended the left side lip opening
so as to be ahead of the prop spinner to get closer to the prop blades and
capture more "air" from the propeller. The alternate air valve from Air Flow
was quite large and thus required the forward opening position.  Aparrently
I gained a significant increase in manifold pressure. boost.  The alternate
air picks up air through the filter from inside the cowling.  Ram air is
straight into the flow meter.  Difference in manifold pressure is about 1.9
inch.  Theoretical difference is calculated at 1.2 inches due to air   speed
and compression.  I do not know the equation. Thus there is probably some
reduced efficiency on the alternate air side due to the tight turning radius
on intake.

I use the alternate air on the ground to about 2000 AGL then switch over to
ram air and reverse the procedure on landing.  You notice a significant
difference in performance when changing from alternate to ram air. Also I
use alternate ram air in dusty situations when you seed dust in the air such
as seasonal plowing in farming areas, wind storms etc.

Bob Smiley