Well as it turns out... the slots in the table are not machined accurately. Not only are they slightly off center, but it looks like they were machines in four seperate passes instead of two, and one is not even straight from its mate on the other side of the table. Teach me not to buy a $49 rotary table. LOL.
Tha'ts good and bad I guess. I had to do some hand work on the slot keys on the adapter plate with a file. Now its a very snug fit. No play in any direction. I can drill, countersink, and bolt/t-nut it in place. I should be able to remove it a dozen times or more without losing position. I did mark 0 on the adapter relative to the zero on the table so I can put it back the same every time... I'll need to do it again when I finish it, but for now its marked.