The lowered floor is a great idea, and could be done 'very simply'
with a shaped metal insert in the floor (think oven tray). It would need a thin sheet of rubber sticking on to avoid 'slipping'. I wonder if another inch or so could be found at the rear bulkhead. I can't recall without looking how much space is available behind the vertical wooden panel behind the seat, but if the cross timber frame (along the top edge) can't be modded, you might consider a metal cross frame replacement with a metal panel from that to the floor. If it was done in stainless sheet (like the bulkhead) it would look quite 'normal' and could maybe provide that extra inch. That is not a simple job though.
