What I did was take 2 pieces of 3/4 plywood and screw them together, then took 2 each 4x4 7 inched long screwed them to the plywood, then took another piece of plywood on top of the 4x4. They weigh 3 lbs apiece, so that is 18pounds, was really thinking about buying the lego set, a lot less weight. The plywood on the bottom is 10x10, and the plywood on to is the size of the 4x4.
2011 jayco 33rlds, 2002 Ford excursion, v-10, 3:73 gears 4x4 mine. 2008 Suzuki sx-4, hers. Retired Air Force, now Retired.