This is what the AMA government relations blog says in one of its FAQs:

"Q: Do I need to list both my AMA number and my federal registration number on my aircraft?

A: Yes, you need to list both your AMA number and Federal registration number on your aircraft. We are advocating to allow members to use their AMA numbers. We believe an AMA membership already meets the intent of registration, but at this time place both numbers on your aircraft."

Here's the link: http://amablog.modelaircraft.org/ama...ked-questions/

But the Safety Code doesn't say that, unless it's been amended since 2014. It says you must have your name and address or your AMA number in your plane. It always seemed to me to make more sense to put my name and address (and phone number) in a model, rather than the AMA number, since chances are if it got lost and somebody found it, it would be a lot easier to track me down that way.