Sorry, got a little busy the last few days. Not sure how much ground you want to cover, and exactly the type of roads you or your Hd buddies normally travel, so here's one suggestion:
( and of course, there may be a better route through Md to these roads, but I won't suggest roads I haven't traveled.)
-Day1
Rt 522 south from Pa.passes within a couple miles from the Skyline entrance in Front Royal, or continue south on Rt522 to Rt211 which will take you to the second entrance, with less local traffic entering Skyline. (depends on the dates, of course, but usually I go to the second when I do go there.) Stay at hotel in Luray or Camp, cabin on Skyline Dr.
-Day2
Spend a day on Skyline drive heading south.
-Day 3
And depending on your progress head west on rt 33west to 28 north. (33 has a local favorite section of twisties) Continue up to 220 north through cumberland, Md .
or ... west 33, 28north to Moorefield, Wv, 55east back to Front Royal, 340north to Frederick, Md, 15north back into PA.
Just some suggestion at the moment. 522, 340, and rt 15 vary between 2 & 4 lanes. 15 has the straightest sections of 4laners, but that might be better towards the end of the trip.
There are many alternate ways to go, and can change any thing on the route.
Let me know what you think of this one.
Chris