Richard,

One thing I have to point out is that when you check tp callout you should measure the feature exactly to the GD&T. My understanding on your drawing is: the main alignment is D-B(B1,B2)-C1 and features like E,F,G should have call-out to D-B-C and then there is another alignment system D-E-FG and other holes are called out to this alignment. Therefore, use your main alignment to check tp for E,F,G and use D-E-FG to check other holes that are called out (see my previous post).

Ray Xing
Quality Control Manager/CMM programming
Metrican Mfg., Oakville, Ontario
(905)825-2222 x 250