I had a 10 x 31 fitted a couple of years ago, mainly to reduce noise levels at higher speeds. However, I must say that if I had my time again, I would probably keep the standard setup, which coped far better with the local hills, and speed limits, and would invest the money saved in some higher tech sound deadening for the odd occassions when the opportunity presents itself to go faster than 50 mile per hour!
Editor FP