Well, I got a little industrious this afternoon and
resolved my under-seat storage issue for $9....yes, nine dollars!
If you have an accessible Home Depot, a utility knife (or preferably a Dremel tool), tape measure, a few screws and 45 minutes, you can build your storage as the pictures indicate below...they are removable in 3 minutes with only 2 small screws...
Before (no under-seat storage):
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$9 plastic storage bin from Home Depot (this one is the right width):
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Mark a line 7" down from the top lip and cut all the way around with a dremmel bit or utility knife, then cut the short ends of the bin in half as shown:
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Fit the two pieces in the floorboard and cut the angles to fit the under-seat bump in the middle (this allows the frame to sit flat):
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Flip over and screw the 2 pieces together in the middle for stability, then place in the truck, screw a flat head screw into the plastic cover on each end of the bench seat (they are silver in the photo), then tie the center back to the D ring that is under the rear seat to keep the frame in place (I used tie straps, but plan to use a small bungie once acquired).
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Finished Product:
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This was too easy and more than serves my purposes as they will work with my WeatherTech floor mats that I'm ordering soon.
I hope this helps someone out there who didn't want to drop $180+ for storage.