I began by breaking the flange off the rivet with a small screwdriver between the yoke and frame. Next I removed the remaining rivet flange with a small flat metal file. Then I drilled a #60 pilot hole using the hole in the rivet as a pilot. I then used a #48 bit to enlarge the hole to 1.95mm so that it would pass the 2mm screw.
The picture below shows the rivet with the 2mm screw in place.
When tightening the screw make sure that the yoke will move freely. Use some #2 Blue Threadlock on the threads to prevent the nut from coming loose.
Next I pressed a 3mm washer on the shaft of the mounting screw of the rear driver assembly to give the screw more surface area to stabilize the driver frame and eliminate any slop there too. Again use the #2 Blue Threadlock to prevent it from becoming loose.
Make sure that the driver frame moves freely without side to side movement.
The wobble is caused by the slop in the driver rods on the wheels but the above modifications stop the engine side to side movement. The dual Canon EN-22 motors help a lot too, probably because the driver assemblies are no longer synced with the drive shaft and allows some freedom between the driver wheels.