That's the first time I've heard of going to a lower RPM (higher ratio) sprocket. While it is nice to cruise at a lower rpm, most Harleys are set from the factory to give a nice cruise rpm. I have heard of guys going to a lower ratio (higher RPM) sprocket for the snappy take off (at least on Dynas). But it then makes the criuse rpm higher.
If you do choose to do so, you'd have to put up with the incorrect speedo readout (as previously said) unless you buy a programmable speedo (like Dakota).
I once had larger wheels and tires on a Camaro in my youth, and I was always going slower around cops afraid I was really going to fast.