I also have the California model with magazine disconnect and find using a magazine easier than pushing down on the takedown lever.
I don't know what you mean by the u-shaped sear having play. It has a pivot pin at the bottom of the plastic sear housing and a spring to keep it pushed forward...
I removed the pigtail spring and replaced the outer sear spring with a spring from a Papermate Pro Fit ink pen. It dropped the trigger pull to 9 lb 1 oz. The entire process took 10 minutes.
After surfing through a few times, joined a while back and figured I'd finally post. The latest acquisition was a 4566TSW. Also in the inventory are a post war M&P, model 10, 29, 41, 422, 63, 66, 686, 500, Sigma (9mm) and SW99 (45ACP).