As said above its fine to use the SonR with larger wheels, you need to use with an LED dynamo light nowadays though you'd be mad to use anything else.
The only time not to use it is if you are using for loaded touring as the flanges are spaced closer together building a wheel thats not as strong, also note you have to unbuild the wheel with a 20R for Schmidt to service, but this isn't very often anyhow.
Dave Whittle
SJSC Sales
01278 441542