I'm in the planning stage for constructing a torsion box for a work surface. I've done some research, but can't find anything that addresses what a maximum grid dimension should be. Larger I assume yields less rigidity, but how large can you safely go? I planned on a 4'X8' surface. 3/4" MDF for outside framing, 1/2" MDF for grid, 1/2" MDF top/bottom skins, height of grids 3". If I divide the interior dimensions evenly I wind up with a grid 11 1/4" X 11 3/8". Anyone done something like this and how did it work out?