Thanks to all for the great insights. My marriage may survive this! <grin> The reason I want some kind of cover is for weather and also security. We live near Salt Lake and do get summer thunder storms in the mountains. I don't have a cover and there is no liner in the bed nor do I plan on having a liner.
I don't have a tonneau at the moment but have been looking at the Undercover brand.
http://www.undercoverinfo.com It is one piece and made of composite which means I can actually stand on it, and best of all only weighs 58 pounds so it is easy to remove and hang on the garage wall when I want to haul tree trimmings or furniture.
I haven't looked at the foldable covers but based on comments here, I think I ought to.