The cargo tray did not function well as a fridge slide for me. At full extension, I was not able to fully open the top of my fridge. Also, extending the tray with a fridge and additional gear on it was not ideal.
I was able to diy a gear plate for my DFG fridge slide. Used
AJC Gear Plate - A Modular Cargo Plate for 5th Gen 4Runner - Review as a reference.
Cut 3/4 birch plywood to same size as fridge slide. Bolted fridge slide to plywood using 1/4″-20 thread bolts and t-nuts (6 total). Removed two of the cargo tray bolts/washers. Secured plywood to cargo tray with bolts (M10 x 95mm, I think). The bolts didn't need to be recessed like the AJC plate, as the fridge slide functions fine as is.
It worked fine on recent trip with full fridge. Now, it's much easier to access items in my fridge. It's also easier to pull out the baskets in the fridge. There is some flex, but not enough for me to add another bolt through the cargo tray. Also, I can easily remove the plate/slide and have an intact cargo tray.