Morph-O-Matic & Attach-O-Matic workflow tips?

I'm in the process of making a character who is to have facial expressions done using MoM. However, last time I did a character like this I applied the morphs for the facial expressions to the entire body, which seemed wasteful and generated a lot of lag.

So this time around I had the idea of lopping off the character's head and applying the morph targets to it by itself, then use AoM and an Edit Poly modifier to merge the head back onto the body.

I've run some tests and it seems to work, but it's a little finicky and crash-prone. I'd be very grateful for the advice of anyone who's successfully done this kind of thing.