This should be just under 300 lbs (it adds up fast).  Thanks!

Bill

If you have the right cargo straps its easy to tie in.  You hook one strap
to the inside lip of the bed opening on each side of the tail gate and angle
slightly toward the center of the tail gate  and let it hang over the tail
gate  Load the plywood right on top of it all then run the straps to the
opposite side of the bed, hook them to the tie downs on that side or the
post holes in the bed and ratchet them tight. This assumes using good straps
rated for at least 2 times what your load weighs.   Then secure the load to
the bed so it can't "bounce".  Just putting the tail gate up so the sheets
are angled into the bed is not going to secure them in place.  Get smacked
in the a.s and sheets will come out.  Remember you are liable for damage
caused by unsecured loads.
If there were tie downs in the bottom of the bed you could use ratchet
straps and get them tight enough going across the load that they would stay
put.  Look at a flat bed carrying plywood next time you see one.
If they fit in the bed with the gate up, then all you have to do is secure
them to the bed, the gate will keep them in place as far as sliding out.
Personally I wish the front of the bed was a lot more substantial then they
are.  Think 2x4 getting shoved through that front wall and then back of cab
and then through drivers seat.
Ouch.

Whitelightning