Well I assume you do not have the bracket that came with the machine when it shipped so you have a few options. If it is only 20 miles put a piece of wood on the table thick enough to bring the spindle face in contact with it lower the z axis to contact the wood with a slight pressure. On the weights you can get away with heavy duty cable ties to prevent then from swinging around. If you can get at the z axis screw wrap a piece of heavy duty rubber around it as close to the nut as you can get it then hose clamp it in place this will help to stop the screw from backing off and moving the spindle face away from the wood block. The other option is to make a new bracket, I would not go to that kind of trouble for a 20 mile trip however as long as you take it easy on the roads you will be fine.