When done right designing the crate to be used as the pit is a great idea. It saves so much time when you walk into the competition and it organizes the rest of the pit. 612 used to do it but since we normally go to 3 events a year we got tired of paying overweight charges.
This was our old Pit Crate:
http://www.chiefdelphi.com/media/img...2ff66a9a_m.jpg