I have two edf55 units that i have 20-30-3500 ammo BLmotors for. The shafts to do not have a D cut in them, they are round. The impeller hubs that came with the fan units have to set screws 180 degrees apart from each other. I cannot for the life of meget the impeller hub (or prop adapter, whatever its called) centered on the shaft. Can anyone help??? Please, this is driving me insane!!!

Sean