Okay in my various reading on the subject of Dynohubs I read that the Shimano DH-3N71 hubs are not recommended for 20" wheels; however, I haven't read or seen any similar distinction for Sturmey Archer GH6 hubs. In fact, it seems the GH6 was one size fit all from 20" wheels of Raleigh Twenties to 26" of the English Threes. What is the story on these.. Anyone know??