With at least 15,000 miles on the two prototype Commandos, a lot of it as speeds above 100 mph, I never thought it needed a steering damper. The overall structural rigidity of the Commando frame was at least 8 times greater than the Featherbed. I know because I tested the damn thing! Plus, I was riding a 650SS to work about 50 miles every day!
Specifically, the torsional rigidity (what keeps the headstock in the designed relationship to the rear end) was about 8 times stiffer than the Featherbed. In the vertical bending plane, the difference was about 4-times.
If you have handling problems due to torsional instability, that is the steering and the back end aren't following each other, then there's a problem with clearances or stiffness in the Isolastics. If things are awry in that area, the relationship between the front and back ends can change dynamically, resulting in a very squirrely ride.
I'm afraid the Isolastic design wasn't very robust - we even ran into trouble during development testing. It was a daring concept that was a bit short of practical "shade-tree mechanic" input. When it's "right" there's nothing to touch it in the traditional British parallel twin configuration. Unfortunately for Norton-Viliiers, the traditional parallel twin went the way of the dodo bird and the Japanese multi-cylinder configurations took over the world.
Unfortunately, N-V spent more money with the "image makers" that came up with the green hemisphere tank badges that appeared at the 1968 Motorcycle Show than they did on engineering development. I remember the comments in the weekly magazines - "where's the switch for those green turn signals?" "Was this program funded by the Irish Tourist Board?" (a reference to the green globes, the silver paint and the orange seat cover).
What could have been.
Before joining N-V, I'd owned an Ariel Leader. I found out that Ariel had started work on a long wheelbase Leader derivative with a 600cc 4-cylinder engine, shaft drive, electric start. Unfortunately the engine, even with DOHC and all kinds of clever stuff only got 32 bhp on the test bench. Ariel went belly-up shortly afterwards.
I tried to get N-V management interested in something along those lines. I figured a Commando-based bike with a 4-cylinder, DOHC, 1-liter engine (about 85 Hp), shaft drive, electric start and full factory-installed fairings and panniers, would be a good product. No such luck - they were so locked into motorcycles as a cheap alternative to cars, they never saw the "motorcycles as high tech toys" market. My concept would have been a combination of the 4-cylinder BMW 1000 and the Honda Gold Wing, and could have been in production in 1969/1970. Ah well, that's why I emigrated to join Boeing!