Installing 5th wheel

My question is, how does this install to the bed?It doesn't seem like bolting the rais to the bed, not the frame, would be a good idea. I can't imagine it supporting the weight even if I bolted it thru the bed support crossrails.

Should there be supports across the bed underneath, then drill and bolt? Do the rails goe under the bed and then drill holes for the hoop legs to go thru? If it should have support, what size? 2x2 box bolted to the frame?

Also, should it be centered over the axle, or slightly forward?

The rails go inside the bed. You should have 4 pieces that look like angle iron about 3 inches long. They go under the bed. The mounting bolts go thru the rails,thru the bed and thru the angle pieces. The angles then bolt or weld to the truck frame.The papers that came with the fith wheel new gave measurements to mount in the different brand trucks. I assume you don't have the papers but I think you can get them online if you know the brand and model of your fith wheel. If it happens to be a Reese 15K and inatalling in a F350, let me know and I will get measurements from my truck.

Peavy