I dont think pressure works that way. if you pressurize a hose and poke a hole near you finger and one near the spout both would flow the same amount because the pressure at each point is the same even though one closer to the source. look at our intake manifolds for the srt6's for example the inlet on the back of the motor and 3 runners per bank. The third runner doesn't flow any less because the pressure is equalized in the manifold even though each runner is a different distance from the source of the pressure.

So placing the Regulator before or after wont yeild any difference in the rail. Redesigning the whole rail just isn't required at his point on a stock supercharger. We only need a little more fuel to get the appropriate fuel with these overdrive pullies.

From what i can see aeromotive makes Rising rate regulators that can replace the stock ones. These are adjustable so we have the same fuel pressure during vaccum but get rising fuel pressure once boost sets in. and can be placed before the rail.

Aeromotive|13301 - Universal Bypass Regulator

I dont doubt you the stock design of the rail has limitations but just boosting the fuel pressure a few points is all that needed at this point.