I snapped some pictures of the system I rigged up for the Trillium
1300 that I am restoring. I purchased some car dollys on sale at Harbor Freight that I use under the frame just behind the axle
. I had to place wood on the dollys and drill a couple of holes in the wood to clear bolts on the frame. This distributed the weight
and kept the frame from sliding on the dolly (you can see 2 pieces of wood that are screwed together). I just used a simple appliance dolly under the tongue such that the frame is level. I tried to minimize stresses on the frame.
It is important to note that using this type of a dolly setup makes it so you cannot easily pick up the tongue (it doesn't rotate like the trailer normally does while on the wheels). Trying to lift the tonque would put a lot of stress in the frame, so I've always worked to keep it level.
This setup keeps the bottom of the axle
bracket about 1/2" off the ground and lets me push the trailer in any direction. I push it out of the garage to work on it, rotate it around in the driveway so I can always work in the shade, then push it back in the garage when I'm done.