Replace everything with whoopie slings. I'd recommend tree straps and soft shackles from whoopieslings.com. it's all light weight, won't stretch, is highly adjustable and did I mention light weight? a dutch whoopie hook on the end that connects to the hammock is also a great feature. You need a continuous loop at each end of your hammock for this but it's worth it. If you ever set up with your head one way and decide to switch, all you have to do is unhook the hammock, reverse it and hook it back up again.
I had a WBBB and the straps with buckles did slip a bit on me too; I switched them out to whoopie slings and that's no longer the case. Seriously guys, tree straps, soft shackles to connect your whoopie slings to the tree straps and you'll have the lightest most versatile suspension you can have.