The current interpretation from AMA (and mind you, this could change .... several times yet) is that control line models do NOT need to register, unless they use RC for throttle or some other feature. I have emails from FAA staffers who also say that control line models are NOT considered to be UAS and thus do not need to register. So given these two sources, I figured the prudent thing to do was to go ahead and register, which I did while it was still free. It took about 5 minutes and now it doesn't matter if we do or do not need to register. Now it costs $5. The MAIN reason I registered is because I intend to fly at the NATS again this year, and I don't want a last minute decision by AMA to REQUIRE registration in order to fly at contests or the NATS to bite me when I get there. If not for that, I would not give it a second thought -- there is no way for FAA to enforce registration on control line models since there is no way for them to detect when and where it is happening.