I bought a new Bonnie dart fly screen with the same intent to fit to my Commando. If you have standard "ears" the screen brackets will foul the clocks and the screen will be forward of the head lamp by too much. The stock distance from the centre of the headlamp bracket bolts to the centre of the fork line is @3" , it needs to be about 4@1/2 " to clear everything properly .in the end I fitted the dart to my T140 that has them cast alloy h/lamp brackets that are sold everywhere . Obviously you can remake the dart brackets to fit a Commando, it is just a bit more complicated than it would first appear, still, I'm gonna get another and sort it out for the Norton.
sam