Well, after searching through numerous PA DMV web pages, I gave up and called 2 local State Police Barracks to ask them... The first one said they didn't know and gave me an 800 number to the automated license renewal center(he said they would know, but the was no way to get to talk to a human...
). The second barracks looked it up and said there was nothing in the vehicle code about it, but to be sure I should talk to an inspection mechanic... Knowing some of the local inspection mechanics around here, they wouldn't even notice it on the tailgate...
Oh well... I hate to try to get away with it just because the police don't know if it's legal or not...