This is just a concept sketch of the driver step for a 4 phase driver. We add the 4th phase, but I only use one current shunt on this. The width is ca 33 mm using the same trick in mounting a 4 pole 5.08 pitch connector on the back. I need to adjust this and find space for the 6-wire motors so will play around with ideas for now. The size above is ca 33mm x 23 mm , so an actual controller in 35 x 50 mm size might be possible.