Thanks for this, Matt. It tallies with my on-the-road findings, comparing speedo reading against sat-nav reading. When I changed from 15/44 to 16/41, I was puzzled to observe that I had the same discrepancy of around 6% faster between speedo and sat-nav, whereas I was expecting the speedo to now read up to 10% slower. But it read exactly the same, which is logical if the signal picks up from the rear wheel sensor. (Frontline please note)
I totally love this new gearing. I now have six useable gears and can decide between economical mileage-crunching cruising or blasting around the twisties. It still does everything I want with loads of grunt and endless pulling power - I am simply in a different gear than I used to be. Overtakes are delightful, since I can hang on without having to tread into another cog mid-manoeuvre. Highly recommended.