You'd be surprised.
my rifle stock had a .140 TP with a throat of .204 and an inlet of .240. With the hammer and sroke settings I had, I got a valve open travel of .1143".
The inlet and forces of the hammer dictate this. A .240 inlet has 144.76lbs of force on it. This stroke will allow .212ci of air to flow for this shot. Lets say that you have an inlet that is .002" smaller than mine(.238"). That will have 142.36lbs of force holding it closed. This will allow a travel of approx .1162" thus flowing .220ci of air. My resulting velocity is 883fps. Your resulting velocity would be 900fps. That is 17fps gain for .008ci of air at the same psi fill and the same hammer strike. The duration that the valve is open is less than 1milisecond and the projectile is engaged with the bore for about 2.2ms. As the psi drops the valve opens further and more volume is used thus efficiency goes down. This is why mechanical valves have the curve. A valve will not flow any higher rate once the opening stroke exceedes 1/4 of the smallest passage diameter. For me that would have been .035". Ideally, to open the valve .035 and hold it open long enough to flow precisely .212ci of air would have given the best efficiency, rendering the most consistency and the highest shot count. As the psi drops in the reservoir, the duration would have to increase to accomodate the volume requirement to achieve desired velocity. This is how electonic valves work. Mechanical valves don't have this luxury of modulating duration. Instead, duration is a function of stroke, so to get longer open time, we open further than the requirement for max flow. With the above example, you can see how very minor deviations can affect the valve of a PCP. Minor manufacturing variations are what give our rifles the since of individuality.
Seems like you got one that is closer to the magic combination of inlet, throat and TP than the rest of us. Don't strip out the choke screw again. It seems by your discription and the problem you are having with the stipping of these adjustments that you utilize the screw in a big way to get the velocity you want. I would suggest that you try and hit the start and end velocity that you want with the port wide open, perhaps just slightly high, using only spring tension and stroke. once you achieve the desired output, then use the TP choke to flatten the curve and very fine tune the velocity. I think that you'll find a bit better efficiency this way. You are correct in the assumption that the psi drop accross the valve it altered with the change in TP choke, thus altering volumetric flow. The spring tension and stroke are much more fine than the choke screw. This is because we are altering both energy to open the valve and the momentum that dictates the duration of the valve which are the root of the volumetric flow. The choke is simply a throttle. If your cars fuel pump did'nt put forth enough fuel to move it at the speed you wanted, it wouldn't matter that you had the peddle on the floor. On the other hand, if you had no throttle and you car ran on what ever the pump put out, you'd be going 170mph every where you went and the idle would be annoying to say the least. The idea is to have a enough fuel and a pump to deliver it at a rate that is very close to the throttle position that you want to operate. tuning a PCP is like walking a razor blade.
It is a dangerous proposition to believe that you can reason with evil.