[Geo]

What are those cross pieces and where did you get them. They don't look like the IKEA cross pieces. What are they called so I can google them.

It looks like Boondox is using Harbor Freight loading ramps. They are a popular alternative to the Ikea Skorva bed rails. It all depends on how you want to construct the bed, and availability of materials.
Harbor Freight loading Ramps

My Transit bed uses the Ikea Skorva bed rails attached to 2" wide x 1/8" thick aluminum that are lowered using an additional 6" wide piece of aluminum so the top of the mattress is below the bottom of the rear windows. If you want the mattress higher for more storage under the bed, just attach the 2" aluminum directly to Ford's mounting holes. Plus Nuts and hurricane bolts secure the aluminum pieces to the van. The Ikea rails are screwed into the aluminum to secure them in the moving Transit. Plywood is then screwed to the Ikea bed rails to support the mattress. It has worked great for over 32,000 miles.