I've been building and tuning 1911s since I was 12 or so. My .02 on leaf springs is that 99% of the time, you cannot do better than to buy a Cylinder and Slide light sear spring, and just plop it in. I could swear they are standard Colt, but perhaps they have some vudoo. Anyway, you cannot tune a Wilson, Wolff etc sear spring better than the C&S one.
From there, most of your work should be on the sear itself in doing a trigger job. With a stock SA hammer, you might need to square up the hooks, and shorten them down to 20 thou, but you would probably be better off replacing the hammer with a tool steel Wilson or Harrison (or any other, most come out of the same Extreme Engineering shop, though not Wilson.) They will be square and twenty. I think you can get a sweet pull at 20 without trying to shorten them to 18, at which point you are tempting fate.
With the sear, you kind of have to learn what kind of pull feel you like. The two basic jigs are the Brown and the Harrison radius. I like the radius feel, and think that you can get a better feeling 3.5 lb trigger with that than you can a 2.5 lb trigger otherwise. Just go slowly, and make sure you stay square. Use a lot of sharpie.
Anyway, I think you are a lot better off tuning in that manner. The leaf spring allows you to lighten the various stages of the trigger, but what makes a 1911 sweet is a trigger that has no creep and is crisp yet requires only a gentle touch. You get that through geometry, not spring weight.
Also, make sure your trigger bow isn't dragging. That can cause a lot of extra weight for no good reason.
