Great work! I need to get myself a fridge, though the cooler works for now I guess.
I had actually just built my own version of a rear cargo drawer:
As is, I have about 80 lbs in the drawer. I can't see storing over 100 lbs ever.
In case you haven't thought about this, I used retaining pins (made for sliding doors) on the side of the box that engage detent holes in the drawer (to hold the drawer in or out). One is visible in the pic below.
I also wanted to retain use of my under-deck storage tub, so I had to build a small hatch.
I left a small cavity between the seat and the drawer. I will be mounting an inverter, a compressor, and a small deep cycle battery back there.
Cheers!