See the city’s plans above. Although the City and other’s claim that the stones may be too fragile to move, apparently drilling into them for the insertion of steel pins is perfectly safe.
ariel view of new installation will take you to a PDF file showing an overhead shot of the proposed Queens Plaza greenspace. If you magnify to 75% or 100% you will find the millstone seats in the upper right depicted as two spoked wheels near a bend in the road. One is within a few feet of a bicycle path, the other is under a nearby tree.