We're going to add on too, but I'm still having a hard time deciding between AKL and SSR. How did you decide?
We just did an add on too ... at SSR. Just like you, we debated on AKL vs. SSR ....... so, I thought I'd share a bit about our decision making process.
First - We absolutely LOVE SSR!

It is truly our home-away-from-home!
So, in making the decision about ownership, we had to look at the #1 advantage of your home resort --- Booking Window! That's pretty much it. Unless I missed something, the primary benefit of your home resort is the ability to book
that particular resort only at the 11 month window vs. the 7 month window. We've not had a problem getting what we want at 7 months for the other resorts .... so far .... but our requests aren't too difficult.
Since we alreay knew how many points we were buying,

we then had to look at the points chart to determine if that amount of points would be worth owning at another resort - solely for booking at 11 months - or if we would be better off adding at SSR?

FOR US ... it made more sense to add at SSR vs. making a "new" purchase at AKL. We weren't buying enough additional points to really take advantage of the 11 month window elsewhere, so splitting ownership didn't make sense. We now have enough at SSR to book a GV at 11 months, should we ever need to!
Remember - in order to book your home resort at 11 months,
you must own enough points at that resort for the entire booking. If you are combining points from multiple resort ownerships for the stay, you must wait to book at the 7 month window.
Since you posed the question, I just thought I would share what happened in our house. Best wishes!!!
And ........
Welcome Home 
to all our new neigbors!!! We can't wait to be back at SSR in December!