One thing I notice about the dual drive P24, although technically it has 24 speed, in reality I consider it a 10 speed as most of the speeds are duplicated within two inches or less. Still, it is nice to have those two extra lower gears that make even the steepest climbs effortless. Another nice feature is that one can, most of the time, keep the chain in a straight line in a middle sprocket and change the hub gear as in a three speed. Lots of options.

Sorry I can't help with the caliper reach. Try the mechanic forum. I don't think anyone is interested in reading this thread other than you and I. It seems like we have the entire Mezzo owners collective here. All two of us.