I just got it, and how close can it get to the armor cap with 100 smithing?
The higest you can get any armor is a rating of 567. Seeing as all the Stormcloak armors are crumby light armor I'm not sure it can offer much protection. If you don't use alchemy try and get your hands of Enchanters Elixir and make some smithing gear. Then find some Blacksmiths Elixir to work with your smiting gear and upgrade your armor as much as possible. Or wait until 1.9 hits so you level up more and starting leveling alchemy and make some OP potions to force that light armor to 567.
One thing you must always remember is that Smithing and enchanting are the two most useful/powerful skill in the game. Always use them.