Not using a regulator at the rail is fairly common on newer cars. Ford uses pwm pump control to maintain pressure, and save wear and tear on the fuel pump. No regulator with this style system.
The problem using a mechanical regulator in the rear, is you lose some dynamic fuel control.
Manifold referenced regulators cut back fuel pressure at low load, and increase fuel pressure at high load. This allows a tad bit wider pulsewidth at idle, while delivering less fuel, which can be helpful if you have large injectors. It also gives more fuel at higher loads with lower pulsewidths.
Unless you plan on pwm pump control, the fuel pressure sensor really is nothing more than a logging benefit. It will have no effect on fuel control.
I may not be interpreting what you are doing correctly.