No matter how many bolts or set screws you put on this joint, it will move, thus wear. Movement, to a certain degree is neccessary in this dynamic machine. If you stop the movement in these joints the loads will be transferred to the aluminum beams and castings which will not hold up to periodic loading very well. Aluminum is not good in fatigue situations.
The best solution seems to be the method that allows, but limits, the movement and can be easily and cheaply replaced periodically. Soda can shims seems a pretty elegant solution to me.