UOX 4.0g experimental:
edit: It's very likely I misinterpreted this: viewtopic.php?p=10599#10599
I'm sorry about that.
Clothes don't seem to get factored in when it comes to encumbrance:
Undress
pick up some heavy stuff that makes you carry... lets say 1 stone less than your maximum capacity.
Put clothes back on.
Walk around, see yourself not getting encumbered.
You should be able to always carry maxweight+clothes(/armor?), no matter in which order you pick up stuff. Oh, clothes need to be on your body btw, not in the pack.