Can anyone recommend the best way to show an MPH reading on an MC21

2 options I have are:
take the speedo apart and overlay the KPH values with the correct MPH equivalent. I'm not worried about the odometer staying in Km's
Overlay the glass with an MPH sticker.
Converting 80 to 50 and adjusting 10mph for every 16kph difference is doing my head in. Great for mental arithmetic though !!! OK so 30 is 48 and 70 is 112 but .......

Phil M
_________________
MC21R ; MC21SP , plus some other none Honda 2t's