Here it is a week before Nats officially starts, and I still haven't registered.
Here's my gambit: If I sign up today, I'm guessing I'll be one of the first riders off for the TT. If I sign up at the race, I get to be one of the last riders to ride the course. The benefit being I will pretty much know what time I need to beat, and I'll be racing on a course that has been well defined with lines and faster.
Here's the doc on call ups: