The R&M website has replaced the Dual Drive Birdy with the Birdy Touring. Instead of the dual drive, they have 9 speed 9-32T cassette. But I couldn't find information about the hub or the list of all the cogs. The page only states that the cassette is from Sunrace. I'm curious about their spacing. There would be big jumps somewhere. Alternatively I think it may be possible to fit 11-34 or 11-36 on as small as 16" wheels with a Shimano Zee derailleur which has a very short cage.