G'day Cruz,
I am very happy with the drawers, but one change I would probably make would be to use lighter RHS tube. I built these with 25mm and it does not need to be that heavy, even 20mm is probably overkill depending on how much bracing you use.
One drawer is mine. I carry a battery charger, snatch strap, two bow shackles, tyre repair kit, tow rope, ice cream container full with assorted light rope and occy straps, a large plastic box with spare screws, nuts, bolts, fuses, globes, jubilee clips and anything else small enough to fit in it. I have a briefcase size container with my main tools, a small metal socket spanner box with metric open end and ring spanners, a plastic box socket set and a roll of screwdrivers and all up probably weighs around 30/35kg.
The other drawer my wife has claimed and holds all our survival gear, coffee, sugar, cups , thermos, water bottles. We also store our wet weather gear, binoculars, cameras and other gear when we are travelling. Side pockets have my second battery one one side along with my jumper leads while the other side holds my compressor. This can be removed so if need be I carry a jerry can in the pocket. I have thought about fitting a water tank in the pocket at the rear of the tub but cannot decide on size or material.
The rollers have had no problems at all. The hardest thing was lining them up especially the centre ones as there is a roller on both sides of the support. They carry the load well and allow me to remove the drawers if needed. The same with the fridge slide. I have purchased a 3 way fridge that is larger than my 40L Waeco but because the feet on it sit on the slide I can still use it as normal.
Go for it, mate. It is worth building your own. If I can help any way, just ask.
Paul