I use Wolff 16# recoil springs in all of my Wilson 5" 1911's with no problems. Two guns now have 2500 rounds each and the others about half that many. All guns are running great. My range bag always contains at least one spare 16# Wolff spring. The last time I asked, Wilson was also using 16# Wolff recoil springs in their new 5" 1911's.
16# seems to be what most use generally for a stock .45 running factory ammo. Alan, the throating you are having done on your Kimber barrel, assuming everything gets done right, should help. From what I have learned, that little gap between the barrel throat and separate lower feed ramp is one of the major issues in FTF's with 1911's. It's possible something in this area was a bit rough out of the box. Watch that Wilson 1911 building video again as it has an excellent section on this. If you don't have it, I have a copy.