Here some interesting discussions about racer - mini quads

FPV Racing using Arducopter by Leonardthall
http://diydrones.com/profiles/blogs/fpv-racing-using-arducopter?xg_source=activity

Sub 250gram Autonomous + Racer APM Based FPV Micro Project By Edgar Scott

http://diydrones.com/group/arducopterusergroup/forum/topics/sub-250-fully-autonomous-racer-apm-based-fpv-micro-project?commentId=705844%3AComment%3A2189660&groupId=705844%3AGroup%3A394475

A detailed look at Pixracer by PX4

http://diydrones.com/profiles/blog/show?id=705844%3ABlogPost%3A2170634&commentId=705844%3AComment%3A2206983

PixRacer with Ardupilot by Randy

http://diydrones.com/forum/topics/pixracer-with-ardupilot?commentId=705844%3AComment%3A2191135

Building a Light Weight 250 FPV Quad Using the Worlds Strongest Affordable Material by Forrest Frantz

http://diydrones.com/forum/topics/building-a-light-weight-250-fpv-quad-using-the-worlds-strongest

Worlds Best ESC - Making it Better by Forrest Frantz

http://diydrones.com/forum/topics/worlds-best-esc-making-it-better