Remembered Mating Constraints - Center

[scotty7]

We have put our standard parts out taking advantage of the "Remembered Mating Conditions" functionality. However, trying to do 'O' ring seals this way seems to be preblematic. If I align the central axis of the seal to the centre of the seal groove the constraint is remembered, but trying to do the axial constraint with a center 1 to 2, picking a datum plane in the centre of the seal and the 2 faces of the seal groove, the constraints go in OK, positions OK, appear in the mating Conditions dialogue box but UG will not save it as a preferred mating condition (seems to save 1 to 1 Centers OK). I can check in the File > Properties > Part File tab to see what has been remembered. Anyone else see this, or know of a way round it? Seems to be the case for NX2.0.4.2 and NX3.0.3.2.