keke,
I bought them last year with the intent to change the gearing, but got very busy at work and have not found time yet. Did take the bike out and must say it rides nicely but do find I spin out without much effort and certainly without any significant reward in speed. Great if you only want to take a leisurely ride. I ride with a 10 year old so that is fine with me for now. I do find I ride my 6-speed Brompton the most only because it's the easiest to put in the car with my son's bike otherwise you have to get the rack onto the car.
You can do a search, but I believe there are a lot of satisfied owners of the Mezzo D9 & D10 on the forum.