If the fuel rod is depressed 5mm, fuel delivery will be constant regardless of whether it took 5psi at the diaphragm to depress the rod 5mm, or 20psi.So if understand correctly the position of the fuel rod as dictated by boost pushing on the diaphram will not affect the fuel delivery to any significant amount.
I thought if you are cruising and boost is 10 psi the fuel pin will be depressed (guessing) 2/3 of full travel or 2/3 up the ramp on the pin. I believed that the farther down the pin travels the more fuel ( richer mixture) the engine would get.
Fuel pin travel may not be linear. 5 psi is not necessarily 1/3, nor is 10 psi necessarily 2/3.
You are correct in regard to fuel pin travelling further down equals richer fuel mixture
one benefit of the boost compensator is having capacity to tune when the fuel rod shifts.
You can adjust preload on the diaphragm spring. more preload on the spring means you need more boost to get the fuel rod to move, which delays the addition of more fuel.
If fore example, you need 7psi at the diaphragm to overcome the spring rate and preload, 5 psi will mean the fuel rod is at its leanest position.
At 7psi, it will start to shift.
The deeper it moves the more psi is needed to overcome increasing spring rate as the spring is compressed.