I shoot at 190. From there, I "squeeze" the butt with my tongs to test the tenderness.
I plunge the butt with the tongs - more satisfaction that way. On 3-2-1 I've been invariably finding "fall off the bone" ribs, even with St. Louis cut. With St. Louis cuts I think you can safely back off 30-60 minutes in total across any of the stages. If you leave the breast bone on 3-2-1 is probably more like it. Anyway - my experience only.