Hmmm.... post didn't seem to show up in my subscriptions....
Anyway, yes, the two truss rods are accessible underneath the cover on the headstock. I've found that adjusting them can be a bit of a "black art". On my B12L, the bass side rod provides the bulk of the tension while the treble side is just snug enough so that it doesn't rattle. It also appears that the bass side rod serves to reduce the bow on the treble side of the neck and vice versa, which is counter-intuitive. To start, I'd suggest simply tightening both evenly, just a little bit at a time, and see if that puts the relief where you want it. Might also help if you provide a bit of assistance by pushing the neck a little manually.