Richard, I see your revised drawing and I think I understand your dilemma. You have created an alignment D-B-C correct ? But your true position tolerance is referenced to an entirely new datum structure D-E-FG. B1-B2 have created your axis alignment and your origin in that direction in your original datum structure. Now you need to create a new alignment where F-G create your axis alignment, but your zero stays with datum E. Are your datums E, F & G toleranced back to the D-B-C datum structure?

Bill Reilly
Quality/Technical Manager
Quality Inspection Technologies