Get rid of spreader slop by installing these aluminum plates from Hall Spars! Basically you remove your spreaders and spreader bar. Pre drill two mounting holes in the mast (both sides) on the aft side of the spreader through holes. The plates are maneuvered into the mast and held in place with your small finger while you screw it in place from the outside (alighted vertically).
The idea is to mount them so they overlap the elongated spreader through hole (making it a smaller opening) and provide a tight fit for your thru bar once again. It is a relatively cheep and simple fix, but the plates do wear and may need replaced in the future to keep things tight.