Lots of flying fields that overfly farmland. A good plan might be to consult the AMA accident/insurance fiels to review gas engine crashes that resulted in fire. Then again, with the amount of insurance coverage for a covered club and site, I don't know of too many farmers where that coverage would not easily extend to about triple the value of any given harvest.

I think the OP should go back a little deeper (the people) into the origin of his club though. The farm field thing was an excuse. The people that started the club did not like gas engines and the planes associated with them at the time. Fire was just the excuse needed to exclude gas engines.