Be careful Olly that design of top mount has the circlip on the wrong side for running that way up. Bit shocked at the butchery! You can get alloy eccentrics for novas that run the way up you want without the need to cut anything and will give you all the adjustment you'll ever need.
Dialing those in that much will give about 5º- by the looks of it and a handful in a straight line ;o
If you speak to Leda they should be able to hook you up with the nuts I described dawg :)
filing Knuckles is the last thing you want to do (even if it has it in the Haynes manual :o ) you get miles more adjustment doing it with the nuts plus the peace of mind reliability wise too.