My first attempt to glue the ply bearing pads for the hatch supports was a failure. The pads have to be (and weren't) EXACTLY level in all directions. Even a very minor misalignment of the pads results in the supports noticably not standing/lying straight and thus not lining up properly for the slide tracks on the hatch.
Also the heads of the 10 mm slide bolts were about 6 mm thick, and together with the insulating nylon washer I needed about 8 mm between the coaming and the supports. Because the bearing pads were (as per plans) only 6 mm thick, the bolt heads rubbed against the coaming.
I hacked the bearing pads off again, and made new thicker (10mm) pads and a MDF jig to glue the pads properly aligned. Overkill? Maybe, but...
....this time the supports alligned beautifully. My home-made slide-tracks and slides also work well. I'm happy. I put some 600 gr glass on the pads to strengthen them, as ply alone will probably wear down (too) fast.
I want to drill all the holes and make all the inserts before fairing the outside of the hull. One of the last pieces I have to make before fairing the outside are the inserts for the mast support. Here is my mold (one sideplate removed): I use the two metal studs to keep the tube at the right angle in the mold.