I am lost trying to program datum A (see attached dwg).
As for datum B & C I used a line for each; although I am not sure if that's the best way to do this. The radius is not constant on the part, and there is also a sag in the middle. It is shaped somewhat like a saddle. The part has no planar surfaces with exception to the edges and the mat'l is .025" thk so probing accurately is difficult.
Any advise is greatly appreciated.