Spistols
Seems your issue is revolved but I think it was Bad-Man-1 or BMCM that had a really great dissertation on how to determine the space for the recoil spring. I seem to remember it was counting the coils, measure the coil thickness and multiply those two together to get a compressed spring length. Then measure the flange on the guide rod and the length of the area on the slide in the retracted position. Subtract the guide rod flange thickness from the length of the retracted slide and that is how much you have for a spring. If the spring is longer than the space it isn't going to work or will (?) damage something. Now don't hold me to this exactly but I'm sure you get the idea. Maybe another member can elaborate on it better than I remember.
Take Care
T&B