Have been out of the SolidWorks world for awhile. The new forum is going to take some getting used to.
I frequently see the primary datum for a hole-pattern placed on the actual surface the hole is on. In fact, this is how I was taught to do it. It seems to me that this is impossible to check without a functional gage, and that the primary datum should be on the surface opposite the one the hole is on. I spent some time looking at ASME Y14, and at first glance, the datums (data?) look to be on the hole surfaces. But after doing some detective work, I'm about 75% sure those figures are first-angle projections, so I didn't trust that conclusion. I'd like to hear what the experts think.