Jim you sound like you know what your talking about but sweeping elbows make a significant difference in my opinion, not only can they flow up to 30% more water with the same plumbing scematics but they also will usually save you about 20% in eletrical costs by reducing the friction.

Here are some examples:

Two elbow types and three pipe sizes were used to illustrate the importance of correct plumbing.
Study the results below to understand these principles:
Elbows vs. Sweeps
Flow vs. Pipe Size
Vertical Head vs. Total Dynamic Head (TDH)
Pumping Cost vs. TDH
NOTE: Centrifugal Pumps (not self priming) perform best with flooded suction (pumps filled by gravity) as shown. The suction pipe should be nonrestrictive. To control pump’s output, put a valve on the discharge side.

Friction Loss in PVC Pipe
From the chart at left, using gpm and pipe size, find the friction loss per 100' of pipe.
Example: 40 gpm in a 11/2" pipe = 10' loss per 100' of pipe. 40' then causes about 4' of head loss.
Next find the friction loss caused by the fittings. Please note that the friction loss depends on the fitting diameter. A standard 1.5" elbow is equal to about 4' of pipe; long elbows, sweeps, and 45° elbows are equal to about 2' of pipe; straight through a “T”, about 3' of pipe; and a 90° turn through a “T”, about 9' of pipe.
Example: 40 gpm through 5 standard 1.5" elbows = 20' of pipe, which equals 2' of head loss. Add this to the pipe’s head loss and the actual vertical head height in feet to get Total Dynamic Head (TDH).


Hopefully this helps a few folks out...

edited for accuracy