Rear passenger safety. Ford Okanagan 1992

[Sebtaylorbc]

Hi guys.

I have a 1992 ford Okanagan with the high top and cab over. It's rated to sleep 4 and seat belt 6.

2 seats are in the driving area.
2 seats are forward facing at the bench table.
2 seats are rear facing at the bench table.

The table seats are 2 person lap belts, though I only plan to ever have 1 person on each side, and ofcourse to drive without the table in place.

I'm planning to add basic head rests as a first mod. But secondly, I'm somewhat concerned about the strength of the back rest on the rear facing seat. The rear facing lap belt prevents the passenger from moving upward or backward (in the van), but their weight, on impact will travel into the back rest.

Surely the ply, regardless how its mounted, is not strong enough to stop the weight of an adult (or two) flying through into the drivers seat? I've added pictures for context.

Looking for opinions, thoughts and suggestions!

Thanks

Seb