The topper will be installed tomorrow, so now is the time to really start thinking about interior construction.
The image below is the bed of a woman who goes several levels higher in van/truck bed construction with T-slotted extruded aluminum. Check out her materials list.
The Toyota truck camper build will begin with the topper installation tomorrow. So far there are 2 sheets of plywood on the materials list. Defying Normal uses 1/2″ Baltic Birch for the visible plywood, finished with General Finishes “High Performance Water Based Top Coat”. The non-visible plywood was ACX 1/2” plywood, then covered with the same finish.