The PLB foundation, the same one I have, post #5, is the new and improved stronger version. I confirmed this when I spoke to their CSR this morning. She said they went to a 2 beam construction to make it stronger. The problem is that neither of these are center beams, so if you have a steel frame with a center beam, like this one, the 2 foundation beams are resting on the 2 cross beams of the steel frame. A steel frame with 3 cross beams, like this one, would give the foundation better support.
She also confirmed that the foundation has 7 - 1" x 3" (actual 3/4" x 2.5") top slats, which, IMO, are not enough. This is the queen foundation. Not sure how the king foundation(s) are constructed. As I previously posted, this is the foundation I should have purchased.