The is no dual bulkhead guys, it's just an expression, a metaphor.
All RB did is displace the steering mechanism and the hydraulic fluid collectors from the classic real bulkhead that we all know, to the inside of the cell and place them on a virtual secondary bulkhead, a cassette
the internal suspension components remain at the usual spot. The monocoque might be a bit longer and it has a thinner bulkhead thanks to these change now. And the lower wishbone forward mounting point is more forward.
https://i.imgur.com/AhUTOHp.jpg