RE: AMA numbers on aircraft
I've seen two flyaways returned months later, because the owner's address label was on the outside.
For those who aren't familiar with address labels, back before Email, we used a quaint service called the US Post Office. The sender would put his own address in the top left corner. Vendors sold preprinted stick-on labels for that purpose.
Those preprinted labels are still available, and you can probably find an inconspicuous place to put them.
Dave Olson