While it has yet to be challenged that's WRONG! I don't think it would hold up in court once challenged at least in it's current "state" I do admit it's a but more than a suggestion now. New Rulemaking Creates Uncertainty for Model Aircraft Flyers
reg numbers need not be visible on aircraft, merely "accessible" without the use of tools. throw your reg # on a piece of paper, and toss it into the battery opening. done and done.