I've got a pirate shirt for Hiro that I conformed to Aiko3. I wanted to play with magnets to make it fit her, so... Selected chest of shirt, loaded Mag 1, added element to deform (leftCollar), played with magnet until shirt covered her left breast. Selected chest of shirt, loaded Mag 2, added element to deform (rightCollar), mirrored Mag 1. Now both breasts were neatly covered. Spawned Morph Target (named it "Fit A3"). Deleted Mags 1 & 2, and then set Fit A3 to 1. Both left & right collars of shirt popped back as though they had never been affected by the magnets at all. Ummm... whatdidImiss?

Spawn Morph Target must be done for every bodypart.  You also have to dial up the new morph target for every bodypart.  When you see cases of a dial on the Body that appear to do this in one dial, what is actually going on is that the bodypart dials are pulling their value from the dial on Body, which actually does nothing in itself.