I was persuaded to change to a 17 tooth front sprocket and it did make the bike slightly more relaxed at motorway speeds. It also put cruising speed revs at the highest vibration point and after around 20 miles my right hand, wrist, forearm, elbow and shoulder were painful and after around 50 miles were going numb. My osteopath warned me that I was risking permanent nerve damage. So I swapped back to the 16 tooth sprocket and all the problems went away. When you fill up, ride 180-200 miles, then fill up, regardless of which sprocket you have does it really make that much difference? Plus I managed to do the 23,000 miles of the TransAmericas on the standard gearing with out wishing it was different.
I can understand why racing teams change sprockets but do we really need to? The manufacturers go to great trouble to get it right, so why not leave it alone and just ride the bike.