Minnflyer,
you might want to contact AMA directly and check what you said on the insurance requiring an AMA sanctioned field or event. I believed that to be true, but contacted the AMA about six months ago, and was very clear about having the opportunity to fly on privately owned farmland, and that I was interested where AMA's insurance stood on the issue, I was told flat out if I was an AMA member, and flying using all of the AMA's operating procedures, I would be covered. I even wrote back to clarify and said, so if I lose control on private land, and by some chance the plane manages to make a beeline for the one neighbors home, at least 3/4 of a mile away, I'd be covered, and I was told yes. I recall correcting myself in a post some time ago as well, as I had been saying also that you had to be at an AMA site. I don't think that is true.