Might look into rivet nuts (“rivnuts ). Look on YouTube for vids and how to install without expensive tools. Basically drill a hole, install hollow rivet that has internal threads, pull it up to rivet to underside of metal, remove install device (homemade-easy) and bolt down seat bracket😁. Good luck. 

Dan
Country Homes Camper, the Huckleberry Sky

> On Jul 20, 2018, at 7:40 AM, Andrew Berg <andrew@BERGWEB.CA> wrote:
> 
> I'm in the process of installing a rear facing jump seat. I have the bracket mounted up to the battery box and now need to get the floor supports in. I've seen some people just drill small holes in the plywood subfloor to expose the metal floor beneath and then JB weld 1/2" or 5/8" nuts in place. I tried this and even after a 24 hour cure, they pop out as the jump seat is tilted forward to remove it from the van. I think I need to actually weld these to the floor. Doing so would require removal of the entire plywood subfloor. I already have the rear bench out of the van, but I think a row of screws is holding the plywood slightly below the front edge of the cabinetry. Do I need to fully remove the cabinets, fridge, sink, etc. to get at these screws and remove the plywood subfloor or is there an easier way. I was thinking of even using a circular saw and cutting out a portion of the subfloor to expose enough area to safely complete the welds and then screw it back in place afterwards. Ideally, I would pull the whole floor up and then put down some laminate or something nicer later, but it seems like a big job.
> 
> Andrew