Keep making the magnet scale larger until the pants fit. Spawn an MT for each bodypart group of the pants that are effected by the magnet. Name each MT the same thing and create the full body morph later; it won't work unless the regular MTs are in place.

I might go with this, although Id prefer a more rounded front

keep working small areas at a time and spawn morph targets then move to different area...some dont realise magnets are completely interactive and can be adjusted in real time {area of influence} just move graph to side and watch reaction to adjustments... magnets can do some great things given patience and practice

Then delet the magnets, load the morph targets and add more magnets?

Make sure you have your display set to "Full Tracking" and enlarge the Mag zones a bit to increase their effect.

There are three thingies to juggle; base, mag, and zone. I get the best results by first sizing and placing the base, then messing with the size, shape, and angle of the zone (like JeffH says, on "Full Tracking"), then move the magnet around.

heyas; use more magnets. :) once you get it 'mostly good but some parts still stuck in,' then put little magnets on those parts to move them where you want. or, if you hate having several magnets, you can spawn intermediate morph targets (set the new morph dial's to 1), and move the magnets to work on other areas.

What huolong said. Seriously, I was working on a busty Victoria model and trying to make her dress fit without her boobs poking through. With the Vic models, this is a little more complicated than a P4 tee shirt, because the breast area of her dress is subdivided into Right Collar, Chest and Left Collar just like her body. Fortunately someone here twigged me on to adding multiple elements to one deformer. Double click the magnet itself and choose the other elements to add to the deformer: you'll get multiple mag bases, but still only have one mag and mag zone.