Thanks for taking time to help with this. The mast is up but it's shrink wrapped right now so I feel a little handicapped trying to figure out where all the lines are going. Even though I'm no closer to figuring out what the blocks/extra line is for, at least I feel better knowing that its not something super obvious.
Its not the vang (boom still attached with vang in place) and it sounds to me like it was just clipped to the end of the jib halyard for storage. I'm left trying to figure out what else would use a 4:1 advantage for up front.
Unfortunately the seller is unavailable so I'm a little on my own here. I took a picture of the brochure where the blocks seem to be clipped to the cabin top (just behind the shrouds) which makes me think it's a pretty standard feature, so maybe I'm misreading which wire is the halyard (curse that shrink wrapping!).
This is probably one of those things that will be apparent in 2 seconds come spring time, but it just bugs me I can't figure it out NOW.