Jenni's been living with me for 8 months now, and she still has MD tags. My dad was pinging her about getting 'em changed, but we talked to the City of Fairfax, and were informed of a fun little fact: if you're going to school in Virginia, you can keep tags from a different state. Cool! So she
legally has MD tags in VA.
I dunno about any loopholes or other fun facts in PA state law, but I'm sure there's something you could use. Until you find it, though, hope the parking police don't notice your car