For the rear of the helment I have just used the sticky pad mounts. If you would like, when I get home from work tonight I will measure my handlebar mount to see what the max pipe size it will accomodate?
Cheers
Here are a couple of pics. The handlebar mount works great on the handlebars, signal light posts and the swing arm. Could not get it around the hand grips (I don't have an engine guard and the hand grips were a larger diameter) just for reference. If I had screws about a 1/4 inch larger it would fit. It's a very clean mount, not bulky, I like it.
The mount itself with one screw out, just to show that you have the ability to increase the opening. In my opinion I think if you wanted to mount to a pipe 2" and up I'd go with the roll bar mount, same idea just larger.
Hope this helps.