I have done 100 mph several times (the same rules apply in Denmark as in GB, but the police seem to be very few and far apart as I have been speeding for the last 42 years without ever having been caught) and I have at one time done a 150 miles stretch with an average speed of 80 mph. The wh8la2 didn't seem to mind at all.
75 mph seems to be the optimum speed with the RS-fairing mounted, keeping consumption low, vibrations almost non-existent, and travel time short.
greetings from a precipitating north