If supporting at more than 4 points (excluding the wheels), you may find that you need to tighten up some supports periodically due to settlement of the ground. Wedges (like re-sawn cedar shingles) will work if you don't want use extra jacks and use concrete blocks or cribbing instead. Spreading out the contact area to maybe 2' x 2' with the ground by overlaying some 2x lumber or with cribbing made from 4x4s will help. Removing vegetative material and soft soil can help and if needed, put back a little crushed gravel to level and stabilize the ground. I tried a pair of aluminum stacker jacks ahead of the axles but soon found one or two out of all 6 jack points would loosen in just a weekend of use and gave up.
If you have electric stab. jacks, they aren't very good at stabilizing and will need some screw or bottle jacks to supplement them. Some of the motion you feel could be due to side-side movement in which case stabilizer struts will help (BAL Lockarms for ex.). Installing new steps like the Torklift Glowstep will significantly reduce movement when someone goes up & down the steps.
