Yes you can play with six of your own characters but as Melusine said; you won't have any room for NPC's and therefore you will be limited on the XP available to you. Personally I'd only leave two slots max' for NPC's. One for long winded quests and one for the love em'n'leave em quick NPC quests.
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It's bleedin dark down here, slippery too.
Man, that's a pisser.
