- JIM I built the hatches on my North Bay as described above. except I uses only one layer of 3mm ply for the lip, reinforced with glass. if you recess the lip 6 mm then the hatch will be more flush than what I did. remember the reinforce the hatches also. the front hatch cutout will probably spring out some from the curve of the deck. the rear hatch isn't as waterproof as would like (nearly flat)so I think I'll try some screw down device,,by the way,it's a fast boat as .