uox3 98.0.4 g experimental, but have been noticing this since 4.0
3D client 5091 - UO_riced
razor 1
Empty your hands.
Equip two handed weapon/item. now, without unequipping, equip onehanded weapon/item _that would go in main hand_ (so no candles for instance).
You should now be holding both items in your main hand.
The order in which you equip the items doesn't matter, results are the same. You cannot carry 2xtwohanded or 2xonehanded, but 1 of each works.