On the previous (now hijacked) winter champs thread the Tamworth guys stated that practice would be controlled by alternating electric/nitro time blocks (I think they mentioned 20 or 30 minutes) with a comprehensive frequency board, and max of 12 (I think they said) cars on track.
This is also exactly how they managed practice for the recent Tamworth Cup and it worked well.
I'm sure based on the performance of the club at the Cup meet last month they'll be well organised and have plenty of personnel there on the Friday to manage the practice process.