Used gas lift supports for the downward pressure. Rollers made out of PVC pipe. I haven't tested it out yet. This was my first design. The springs would bend and finally break. I put a digital scale under my new design rollers and it read 52 Lbs. I'm thinking it may be too much since the rollers don't roll now, just slide(well at least on my trailer,haven't tried it in grass). My old setup they would roll, but not as much pressure. I think I need roller bearings in the rollers to correct this problem. Any thoughts or comments appreciated.