You can talk to Don Herman
www.hermco.net
His first job out of high school was to cut big sheets of plywood into 5" squares for seavee.
Seacraft hatches are the same and so are almost every other manufacturer . . . big sheets of core material are hard to lay into a mold and will almost always trap air . . . little squares don't bend and distort like large sheets of plywood and that resin grid makes one stiff laminate.