E1 is very generous as far as encumberance goes. Unlike the later games, shields and helms are mostly non-encumbering, so once you have items like the mithril plate mail or airy chain mail, multiclassing becomes a breeze.
As an aside, the cursed studded armor in E1 has a defence value of 65534 due to some kind of underflow error. I've only tested it a bit, so I'm still unclear how effective it actually is.