Since I just mentioned it in my thread about party controls, I should probably give a quick reminder to anyone in favor of a six-members party:

don't overlook giving feedback on the issue of how the party is managed/moved around, because solving it is basically a pre-requirement to actually get the party expansion you want.
The chain/unchain system and its clumsy auto-follow work already poorly enough now. With six men in your party it would turn into an unmitigated disaster.