After doing a bit of measuring I'll probably make a slide out like I have for my Jeep then put a rail over it like Jim B. did, the containers now are lower profile with as much space so its going to work - or I'll make it work.
The advantage to a low profile slide out under the rail is you can keep all your tools in it, snap over locked so they don't go helter skelter while rolling down the road. Cheap carpet liner soaks up any grease or oil and keeps the basement clean.