I'm a disabled poor-boy so money is tight. I'll be building a 6x8' box trailer 4' tall and I'd like to put sliders on the shelf that divides it top to bottom with the bottom 2 ft for large planes and the upper 2 ft for smaller/lighter stuff. I need the shelf to be nearly the full 8' length and slide out approx 4-5 foot so I intend to add supports for when it's extended. Where can I find some slides to accomplish this for a reasonable price?