The round stock served a few purposes but none were structural. I wanted to create a point that separated the outside of the vehicle with the inside. Typically when I do a full sheetmetal bed, I like to do a fully-molded look where the outside of the body flows seamlessly to the inside of the bed. When I think about a C10, I think industrial work truck. The tubing gave me that parting line from rounded body to structural bed. I like wide bedrails, it's something I do on all the beds I build. Installing the tubing added girth to the bedrail and made it easy to keep a long consistent radius.