It's pretty hard to torque everything on a Norton, crows foots and calcualtions go only so far. For me a big help has been to use a tool that I can apply about the right force on. A lot of small bolts I do with a quarter inch drive, I tend to cut off wrenchs for special applications so they work well for me.
I hadn't broken a bolt in years doing this stuff until last year I was torqueing a BMW head bolt with a bloody torque wrench and it let go before spec. Not a death in the family, I was able to repair it with a thread kit, but it did make me more apt to be careful with a big clicker wrench.
If you feel carefully you can often find the point where a bolt stretches.
Some of these guys do this a lot and are not just a hobbiest like I am, I bet they have a lot of special tools they have set up to work for them.
When I worked on Nortons they were new bikes and I was young, so I'll be quite interested in some answers from the regualrs here.
I'm afraid I've forgotten most of what I learned back then although these discussions bring much back. When I was a mechanic I worked mostly on large commercial engines and transmissions, and although a technique works on similar items nothing beats working with equipment regularly.