RE: AMA question
Have you checked with AMA for the input?
I used to hangar my ultralight out of an FAA listed airport called [link=http://www.airnav.com/airport/78I]Pam's Place[/link] and there is an RC club that flies out of there too. I don't know if they are AMA sanctioned though.
I once landed during an RC flyin and had no problems. They were courteous, several landed their planes, and one just flew in a different direction. I could easily see the planes and although I radioed my intentions I doubt they monitored the frequency so they must have been using a spotter. Or, they heard me approaching.
If I'm flying my RC planes at a GA airport I think I would notice an approaching plane and be able to land in plenty of time.