How do you handle True Position with simultaneous Datums?

[[Am...]]

I have a part that is essentially a case with two slots cutout. There is a true position on both slots (different sizes)
where A is the OD of the case. This means that B-C datums need to be evaluated simultaneously correct? How do I do this on Calypso?

[[Cl...]]

The "dash" indicates that they combine to form one datum.
Is -C- 180 deg from -B-? They should occupy the same center?

It looks that way. Based on what I see, you could construct a 3d line
from B&C, and use it for a planar rotation. If -A- is the OD that would
be XY origin, and then whatever plane surface for spatial & Z origin.
Then evaluate -C- & -B- separately.

Someone else might have a different take on this, I've been wrong before.

[[Am...]]

Yes they are 180° from each other, so I can make that 3d line from two symmetry points on the slots. But would I really need to bring in a plane here? as the only plane would be that very thin wall you can see in the drawing and it is not a datum.

[[Me...]]

B-C is a line from the midpoint of each slot. B-C is Primary so it controls the origin in 1 axis, rotation, and technically the spatial, if it's possible based on Can-May-Must. A controls the origin in the other axis and spatial if the slots are unable to.