Ebay's discretionary policy borders on the ridiculous. I once spotted an auction for a drum head "signed" by all 4 members of Led Zeppelin-
Only problem was that that particular head was not made until 1992, and John Bonham died in '80. I emailed ebay telling them and received a long form response that basically said "while you may be an expert in a particular field... blah blah blah...it is up to the buyer to read ebay's policy on autographs..."
They don't care.
Make the shirts- I'll take a few! I'm partial to Ludwigs myself. Boo Gretsch!