The standard Tachihara 4x5 lens board is rectangular according to the Linhof pattern BUT a square board will fit. I made many 96mm square boards out of 2mm aluminium plate.
These boards fit the Tachihara 45GF four different ways so I can have the f stop and shutter speed numbers facing me irrespective of camera orientation.
Another advantage of square boards is the possibility of off-centre mounting of wide angle lenses. My 65mm lens needs tightly compressed bellows but the off-centre mount gives me rise, fall, right shift, or left shift depending on the way I put the lens on the camera.