Mattress air or something else for D3

[ade]

Am looking for a mattress pref air for ease of storage, that fits in the back of the D3 with the seats down flat (two people). What's the best size for fit. What do others use?
Thanks
Ade

[CAR]

I used the sofa bed mattress from the lounge suite once. A little squishy in places, but worked pretty well. I attached a photo. Hope it works.

Apart from that, im pretty sure ive had a double air mattress in the back as well.

[CAR]

Just found this photo too. Pretty sure that was a double air mattress on the bottom.

Had my boy up on his own "top bunk" between the back windows. Plenty of room for my legs underneath and he loved being up there.