I have seen a design for "encoding" drawbars that I don't think will work with actual Hammond drawbars.  Hammond drawbars are NOT linear slide pots.  They are nine position slide switches.  To change the contact closures to an analog resistance value the design uses eight 1.2k resistors in series with with the drawbar wiper switching between the resistors. On a set of Hammond drawbars, each drawbar has it's own wiper but the contacts are all bussed together.  The switched resistor scheme abov