I use a Tubus Fly. It is very low profile, which suits a small frame (though mine is actually a 58cm IIRC). A friend who is vertically challenged found the fly was perfect on his tiny Hewitt, where a tortec rack just looked wrong.
It does depend what you want the rack for though; the fly has a small, triangular top section so it isn't ideal for a rack top bag. It is fine for panniers. On mine it is so close to the mudguards that I had to mount the Smart rear light upside down!
You can see how it hugs the wheel in these photos.
(That's an SQR Tour back on the bike, mounted on the seat post not the rack). I now have flys on both this bike and my Audax bike.