At the moment design is a couple of hinged/sprung boards that cover the apperture when sleeping - they will lift up to allow access downstairs when using the full length bed. But I have lots of other ideas which may work or not. Will see when its all in place. Just like most pop tops have boards that slide into place for the bed, just this one is a little shorter! This design will work, but Im still working on a design which wont involve disturbing each other if we need to get up in the night. TBH at the moment the design is no worse (and probably easier) than clambering over someone to access the conventional ladder system.
Of course there is a twofold advantage (in my eyes anyway) for this system. One is access to tent from within van and removing need for an external ladder. Other is when tent is up you have standing room and even when it is down you have extra head height for a bench seat (just big enough for both of us to sit and eat inside if necessary)