[dsraven]

I know this is a small window cab but here is a pic of what it looks like with the skin off. I would say use a seat with belts in it or do some reinforcing behind there. what if you drilled an oversize hole in the cab where you want the nut anchor point, then slice a hole in the door jamb from the front facing edge and slide in a piece of flat bar (with a hole already drilled in it) then weld the nut to the bar (through the hole in the sheet metal) and cap it all up nicely when done. that way there is something back there at least. make sure to pull the flat bar against the sheet metal before you weld. maybe work?