With the Unhindered Light Armour perk does it mean only the armour you are wearing has no weight, or all light armour you are carrying ie your loot from the latest battle.
In patch 1.4 if you have one base piece from a set equipped, any pieces you are carrying from the set are also weightless.
I don't know if this was true as of 1.4, but under 1.5 it works a little bit differently. Say you're carrying three differently enchanted full suits of dragonscale. Equipping any one of the helmets them makes all three helmets weightless, but not any the chestpieces, boots, or gauntlets. Those will still have weight until one of each gets equipped.