Grim Greaser I need advice on XR-700

In trying to install the XR-700 0231 ignition system in my 49 coupe, I ran into a clearance problem with the distributor cap and rotor button.  It appears that the optical shutter needs to have about  1/8 inch shaved off of it in order for the the rotor to sit on top it and the distributor cap to fit on top of the rotor.  Before I start cutting on this thing (or send it back to the manufacturer), I'd like to know what you did to solve this problem.