So I did my commute yesterday in one gear, and it was pretty comfortable, although I did have to work really hard coming up the final hill. But the thing I noticed is that I have to deal with a lot of traffic on the way home and I'm thinking it might be better for me to have freewheel so I don't get killed. I know that some bikes come with the flip flop hub. Can I just do one of those myself? That way I get the best of both worlds.