Is there an optimal way to use a bolt hole pattern as a primary datum that constrains the proper 5 degrees of freedom it's allowed? 

I have 8 holes spaced evenly at 45° at typical compass directions, all are nominally angled in the Z-Axis. 

If I measure all 8 as cylinders, extract the points, I can create a best-fit cylinder, but this will not control rotation around my Z, whereas the pattern can.  

If I measure all 8 as circles, I can create a best-fit alignment that controls rotation around the Z, but not around the X or Y, whereas the cylinder pattern can.  

Is there some way to merge these two?