I saw an ad for a "drive-on" tandem axle trailer jack a few weeks ago somewhere, but can't remember where I saw it. I have seen the ones for single axle trailers, where you place the crescent-shaped jack under the axle and drive forward until your tire is off the ground. This tandem unit I saw works in that you place it in front (or behind) the good tire and drive up onto it, thus lifting the flat tire off the ground. Has anyone seen this type of ramp around? It was compact enough that it was stowable in your tow vehicle, yet, at the same time, sturdy & heavy-duty enough to support a boat's weight. Help!! Thanks.