It is time to retire my 7 speed Dahon. Sad, but it has served me well. One of the things I did not like about it is that the rear derailleur hung pretty close to the ground. I have seen other folding 20" 7 speeds that have a rear derailleur does not hang so low. If I find the bike of my dreams but it also has a low hanging rear d. is it something that can be easily changed? inexpensively?