Wilfred;
I think that you can use MMC with a Datum " It is a totally natural phenomenon that the larger a Datum Feature bore gets (departs from MMC), the more the part it belongs to may shift relative to the Datum Feature it engages on the mating part. Thus departure of a Datum Feature with size from its MMC induces residual mobility in its associated Datum Reference frame. Since tolerance zones are attached to Datum Reference Frames by Basic dimensions, they become mobile when the Datum Reference Frame does. Permission to take advantage of this mobility for assessing compliance is granted by placing a Maximum Material Condition Modifier behind the applicable Datum Feature label in a Feature Control Frame, and creates what is called a Datum Feature Material Condition Bonus Tolerance."
This is out of "The Little Encyclopedia of Geometric Dimensioning & Tolerancing" BY William Tandler that is based on Y14.5M 1994

John D. Ruys
CMM Programer/Inspector
Teledyne MEC