To tell the truth, the "correct" way to reduce object size to to carefully think out every part when you build the model. Once it is finished and grouped for Poser it is too late to do that much, even in Max. Stay away from NURBs, make high density mesh only where it is needed for detail, don't include any surfaces that are always hidden (many of the original Poser clothes have inside surfaces that are only seen before they are fitted, for example). I know this is not the answer you wanted to hear!