Hi Chuck,
I do agree with your spring choices, except I still like the 18.5 for ball. The cases don't go into orbit and the recoil isn't as sharp. The only metal stressed by that spring is the slide stop, and they're pretty tough. I can't remember ever having seen one break....wear, yes, break, I just don't remember.
On the damage I found. Most of those pieces were WWII vintage, and many of them had the two-tone slides and many were either fully hardened or quite soft. All the other parts were pretty darn good...forged and hardened. The pistols had about every kind of injury you can imagine. From being used as hammers to firing with sand-plugged bores, to just worn-out from training/practice firing. Many had cracked frames, cracked slides usually the front edge of the ejection port, battered barrel recoil ledges (the area just under the hood), battered bottom barrel lugs, broken and/or rounded-off top lugs, both barrel and slide, cracked barrel links, broken extractors, loosened ejectors, broken and/or too short leaf springs (center leaf), and a bunch more. You name it and if it could be broken, it was. Lots of these pistols were match-conditioned and most of the work on them was just replacing barrels, bushings, trigger jobs and tightening the slide-to-frame fit. Of course replacing all springs on all pistols was routine, as well as replacing the disconnectors. I remember one bunch of pistols that had soft firing pins that would batter and then stick in the forward position in the firing pin stop. You can imagine the results of that.
I guess that'll do it. We've strayed a lot from the question of which spring for light loads, but what the heck, it's all educational for some of us. Regards. Bob