I think most people go for the Sigma series (in fact there is even a fitting guide on the main page of vtr1000.org) as they are accurate to something like 180mph I believe.
I havent got one myself mind as I pretty much ignore my speedo most of the time anyway!
Cheers wayne you should be able to see it at the Arrow Mill on 19th.
Don't usually use speedo myself can't see the small numbers, but I want to start training for IAM and will now need to be able to control the animal to closer than open and shut