When the April issue of Model Aviation comes out look for the CL scale column that I just turned in, it covers the rules that are out there and where all of the contests are located.
You can fly 1/2a Scale at multiple events across the country and then of course at the Nats!
These are the 1/2a events that I have found during my research on this event...
Milwaukee - June 8
Brodak - June 10-14
Nats - July 11-13
FCM - Aug 23-24
Sugar Grove, Ill - Sept 14
St Louis - Sept 20
Tucson - Mid Oct
Phoenix - Late Oct
Fred Cronenwett