In order to have no weight, use the steps for unlimited spell effects using the Spell Feather with a magnitude from 100-100 on self for two seconds along with Soultrap for two seconds. After making the spell, cast it as many times as needed to get the desired encumbrance.

Note: Instead of using the previously described long process, get Skull Crusher (recommended) or a Feather Enchanted constant effect weapon and do the same process as to increase skill (hold L + R + X).