I have cut a few mango trees in half, to fit them for transport, so you should have no problem, as for how this will effect a VP over a long period of time I have no idea, but VP is a hard animal to tame in my opinion, and it will probably be hard to keep it small.
I have been thinking a bit on this, maybe someone with more experience can chime in, I wonder if what happens if one cuts off the tap root? or places something solid directly beneath the tree, so that the tap root cannot go downwards . would this not make the tree more dwarfish ?