i was wanting to avoid the upkeep of pine in my bed as well. i looked at the synthetic decking but it was not available in widths large enough for the middle board, 7.5" i believe. i found that black locust is indigenous to NC and is resistant to rot, insects, mildew, etc. other options i considered were Ipe, brazilian cherry, and a few others. It is a bit heavy but weathers to a nice ashy brown color that fits in well with my heavily patina'd truck. i found a local mill that had some and then ran them over the table saw to give the relief to receive the strip. been installed for over a year now and they are holding up great - don't have to worry about scraping the bed or leaving in the rain.
