I have an older JR3 that I just secured to my bench. The bench top is 3/4" ply so I figured I'd need a 2x4 mounting block under it to help secure it. I'm still getting a fair bit of play when I'm seating primers, what should I do? I'm thinking about getting a steel plate that I can drill a pair of hole into to allow the bolts to pass, but I can also use a narrower one that runs between the bolts. What would work better (besides a new bench top)?