Finally got around to drawing up some brackets and sending them out for fabrication today. I'll have four of these, one for each of the four bolts where the front of the rear seat brackets normally sit. The platform will rest on top and bolt into these for support and hopefully prevent things from moving too far if I roll the truck or get in a collision.
Is there a vendor that makes a full platform that actually uses the seat bolt holes instead of just resting on the floor? The only ones I've found seem like they'd be super sketchy in a collision or rollover.