How do you apply datum scheme to curved and irregular surfaces in engineering drawings?

[Goppinath]

1.I believe Datum targets is make sense for this but can we accept this scenario also ?
2. 4X Datum B is applied but in 4 holes which hole axis is oriented with particular datum A face is not clear
3. Can we mention individually for datum A and B ?if not pls suggest better method
4. Datum D is applied at feature but datum feature is at MMB can we accept this ?
5.if we used 4X datum A as showed in image how to establish DRF
plaese help me to avoid confusion

 

[3DDave]

It appears to me that this is a case where the chosen datum features will not force the remaining features into a location and orientation where those related features will meet the requirements at installation. There is some other assembly constraint that is more important and is not being used as a datum feature.

It also appears there are two profile of surface tolerances for the same surface, one that applies "A<-->B" and the other to the entire surface. They have the same zone, so that's good.

The orientation of the holes is to the midplane generated by the 4 surfaces referred to as datum feature A. Because those surfaces represent a taper there could be a dimension from the intersection line or point to the holes, but the basic 155 dimension is a suitable substitute for location along that midplane.