In re using smaller diameter tubing affecting fuel flow: Yes, it will. In Fluid Dynamics, there is a function called CV. Basically stated, given a constant pressure or vacuum, total flow volume thru a smaller diameter tube will be less than with a larger diameter due to friction loss.

Now, in terms of setting up a Perry pump; an (unfortunately ex) old timer who loved these things gave me a procedure that I haven't had any problem with with gas or nitro models. Its somewhat of a pain since it is a two person and a tach (or a good ear) procedure. First, with plane at horizontal, get your motor at WOT and maximum rpm (do pinch test to determine best needle position), tach it. Now, hold plane in a vertical position and tach it again. If no change (OK). If an RPM drop (too lean, not enough pressure), turn the screw in. If your a violent 3D flyer, turn the screw in a bit further to compensate for G forces to increase pressure (200-300 RPM drop at WOT vertical due to richness).

Conversely, you can determine if your pump is giving is giving too much pressure by doing this test, backing the screw out each time until you get the too lean RPM drop and backing off your last adjustments.