RRV Hydration pack question

[Gish]

I recently picked up a Pantac RRV hydration pack to go with my Pantac RRV (http://www.pantacgear.com/pantac.gea...ductid-58.html)

I think i've pretty much figured out the mating of the main straps. From what I understand you config the RRV into the H type, then loop the hydration straps up and over, change the belt buckles and voila.

Just wondering about a few items on the hydration pack. On the rear side there are four thru straps, two of which are bungee. What are those used for?
Secondly theres a strap in the very rear thin pouch. I assume that that would be a holder for a spine plate? (In the real one)

Cheers