My progressive press bench is much like Pavogrande's. It's a 2x4 (on edges) frame, 2' deep and 8' long, 42" to the top of the bench so I don't bend my lower back at the bottom of the stroke. I came up with that 13 years ago. As I get older my back appreciates it.
The top is just a single layer of 3/4" ply but under the ply at the location of each press is a 2x10 that extends from touching the front 2x4 to touching the back 2x4. The press bolts go through the 2-by which is in turn glued to the underside of the plywood so there is virtually no noticeable flex. The bench is secured to the wall with 2 drywall screws 3-1/2" long for solid stability. The ply is finished with multiple coats of oil based one part polyurethane. I think I used Defthane. It has held up very well.
Here's the bench. It's light and strong. The vertical pieces have lap joints for the horizontals to rest on so the load is not borne by fasteners alone. The top is only stiffened under the presses and it affords lots of storage for brass and boolits.