If you see a "Now Entering Maryland" sign it is too late.
OC is well tolerated along I-81, based on my limited experiences. You might get some stares from tourists, but a smile goes a long way towards keeping them calm. Just remember that Cracker Barrel has recently become unfriendly towards firearms owners. But there are lots of other, local, places to stop and eat, buy souveniers, and for other necessary activities.
If you know your itinerary and specific dates, you might want to post a separate thread seeing if there is any interest in a meet & greet.
stay safe.