Putting in a new bed

I've got an old 16 ft stake side flat bed truck with a scissor hoist that ineed to re do. Its a 1971 Ford C600 22k gvwr.
The wood bed is completely rotted out. At one point there was a steel bed on top of it because I can see where they ground thru the stitch welds along the frame edges.

Im got some 2x6 cedar that ill lay in and then 4 sheets of 3/16th steel diamond plate. My question is, if i weld the four sheets together to make a 8x19 floor can i get away with stitch welding the edges along the frame rails? Or do i need to also bolt thru in tne middle here and there?

Seems like the weight of the steel will keep it from lifting up off the wood subfloor but i thought id get some other opinions. I use the truck to haul materials and occasionally up to 5 yards of gravel.
Thanks.

If it lays flat but some how i would connect it in the middle to the bed.

If you just stitch the edges, the middle will oscillate up and down as you drive, not only will the noise probably make you crazy, it will eventually break all the welds. Won't take much probably, a dozen bolts or so would probably take most of the wiggle out of it. YMMV

Mine is 14' 28000 GVWR The flatbed was originally wood. It rotted, I replaced it with 2-1/4" Red Oak. That lasted 10 years. I finally stood 1/4 x 1-1/2" on edge 8" apart, welded them to crossmembers. A single piece of 3/16" 7' wide 14' long makes the floor. I welded around each 4x4x1/4" wall stake pocket & a couple 1" welds between. I stitched flat to ribs in a number of places beneath.
Yes, it now has a new radiator & grill

Alright guys...bolts it is.
Thanks for the info.

The cedar won't last forever & it'll hold water all the time. If you weld on the perimeter you'll hate yourself when you have to replace the wood. I'm 5 years into the all steel version & it's holding up well. I try to keep it at 28000, I don't want fines. I carry a bit of everything, worst of it is a load of boulders. You ought to hear the noise it makes when I dump!