Originally Posted by myredracer
I think the "X" chocks work really well if it's tandem wheels you have. They lock both tandem wheels/tires solidly together.
Seems to me that some of the flex is vertical movement and some is sideways movement. I saw in a magazine a few days ago that one company makes an angle brace that goes from the top of the jack on one side to the the bottom of the jack on the other side. Might help a lot.
As suggested, I think it would really help to put a jack (like bottle jack) under each axle on each side. What the heck, it's only more weight to tow around everywhere. There's quite a bit of flex in the steel frame and if it's just sitting on the tires in the center, you will feel deflection in the frame since there is movement in the springs and some in the tires.
Permanently attach a scissor jack to the tube in front of the front axle on both sides. No storage problem. Jacks from Harbor Freight are cheap and work great in this application.