I'm building up my girlfriend's Gunnar roadie and need a crank and cassette. Since previously she has used a triple I need something that will give her the lower range like a triple and if it sacrifices top-end that okay she never uses the big ring - 12t combo anyhow. We've looked into compacts, I wanted to go with a 50-36 to keep the jump between rings the same as 53-39 but options are limited. So I got to scribbling a little math out and realized that with a 53-39 crankset and a 13-29 rear derrailer it would give her a lower gear than a compact with a 12-25 and not give up much in top-end. Also the jumps between gears would be slightly less than with the 50-36x12-25 setup. Sounds good to me. Here's the rub...#1 Am I missing something, and this would actually be inadvisable? #2 Where to buy a 13-29 cassette for shimano? I've seen Campy ones but that's no good for me. Thanks a lot! I'll post a pic when it's done, maybe even with her on it!