Hi, Im also a former Bongonaut & now in our Alphard we turn the middle seats around & fill the v dip of the middle seats with a pillow each side & put a memory foam mattress topper over the top of the seats. Sleep with feet towards the back door. Very comfortable for us although I'm a short 5ft 4ins.
The mattress topper is quite bulky but fits nicely folded in half in the gap between the front & turned middle seats when stored away during the day. Hope this helps.