I just bought a used Dart Fly screen on eBay to fool around with to see if and how it would work on my Commando without the commitment to having to pay full pop if it didn't work.
The fly screen was originally for the Triumph T100. With a little bit of tweaking, coddeling, and fetling, I managed to get it to work remarkably well.
I'll post some pics later. But in the meantime, here is what I did.
I rotated the instrument housings inwards and reinstalled the instruments one mounting hole outwards. This is to keep the faces straight and to avoid interference with the mounting bracket.
I needed to alter the fly screen brackets just a bit by:
1: Enlarging the hole that the turn indicator stalks mount... needed a larger diameter for the stalks to fit through.
2: On the upper half of the brackets, I cut off the area towards the rear of the split (leaving the bottom intact and the forward upper half intact). This left just the forward half of the upper bracket and full bottom. This still left adequate support for the screens upper mounts. This gave me needed clearance for the instrument to not have to be fully rotated inwards, leaving the indicator lamps and the head lamp switch visible and accessible. I have a '74. There weren't any more holes in the instrument housings to let the instrument be mounted so they'd be aligned straight across if full rotated inwards, which they'd have to be if I didn't modify the brackets.
3: I painted black the raw aluminum that was exposed by the bracket carving.
With all that, the screen fit very well, and looks like it was made for the Norton from the beginning.
JD