Although I have absolutely no knowledge of the rule in question, I can't imagine the AMA would expect someone to only fly turbines at an AMA sanctioned field. If you have your own flying field on your own property, how can the AMA say that if you fly a turbine there, they will revoke your waiver? I think the whole point of the waiver is to prove that you are capable of safely operating and flying a turbine powered model so that you "can" fly it at an AMA field.