Cool! I've not seen those Front Runner mounting rails before, Ryan.
I have South African Front Runner bed rails on my Gen 2 Tacoma, which mount to the C-channels on the bed sides. The rails get used for my ARB rooftop tent. Very sturdy, and beautifully made, as you noted.
I've just finished modifying my old Gen 1 Tacoma Mountain Top aluminium tonneau to fit the Gen 2 truck. (My use case needs a bicycle fork mount more than maker materials, so the one-piece Mountain Top lets the tonneau lift with the bike tray in place. That long-out-of-production tonneau uses Perrycraft Dynasport side rails.
I gotta see if the existing holes in the tonneau might allow those nifty Front Runner tracks to fit... I really like that fitment on your Diamond Back.
-- Don