Rich,
I'll have to open the frame up and measure and count.
I used the frame I had been shooting the 12" .30 cal on, clipped spring with about 14 lbs. pressure as I measure it.
Very similar to what I find in an un-molested artillery, but weaker than the "normal" 18-20 lbs I see in a 4".
As you say, just too many variables; add to that old springs vs. new springs; loose fit toggle/slide vs tight one, and one just has to try it out.
I am convinced that the 9mm is more forgiving of spring differences than the .30.
Helped a lot, didn't I.