Not the OP, but I also have a Decked and a camper shell. And actually have it setup extremely similar with the mattress.

IMG_9888 by
ebeiersdorfer, on Flickr

2017-06-25 17.00.10 by
ebeiersdorfer, on Flickr

IMG_0325 by
ebeiersdorfer, on Flickr

IMG_1232 by
ebeiersdorfer, on Flickr
I've had the shell on for close to a year now and the Decked for maybe 5 months, so far I'm pretty happy with everything. I run with tools, jumper cables, boots, med kit, etc in the right drawer pretty much all of the time. When I'm not out camping or doing anything like that I have the left drawer empty and fill it up with either guns/hunting gear or the rest of my camping gear.
The system is a little pricey though as the one downside. On one hand it's not terrible when you consider Truck Vault or how much a good pair of long drawer slides run. I drew some designs out and came somewhat close in price, but was also going to be double the weight of the Decked. I also don't think I would have been able to get it quite as modular. Back to the price you're probably going to need a couple add ons; I have the drawer dividers to keep things from sliding around and the track tie downs since you loose your mounting points.
Overall I'd definitely pull the trigger on the setup again. Really only thing I'd change is a looking into a mid rise for the extra room. I would have also loved a Flippac or Habitat instead of a normal shell, but that was more than I wanted to spend. It's also worth checking around on Craigslist; there were a number of them around me but unfortunately none for the current gen Ram. Folks seemed to be listing them in the $500-$600 range, kept looking nearly every day for a few months before I finally broke and bought new.