A couple of suggestions for as you get close to Gettysburg:
If your routing takes you from I70 at Hagerstown to Thurmont MD via Route 77 you
cannot take this route. Rt 77 is restricted to combinations of your length due to some blind curves on this route.
If your staying in the south end of Gettysburg and your routing from I70 / Hagerstown takes you west to Frederick and north on RT-15 those are all both major highways and good to travel. But it will take you over two mountains and at least 45 minutes longer. I would suggest you take -
I70 to I81 North (at Hagerstown) to the Greencastle PA Exit #5 Route 16 East. Route 16 takes you through Waynesboro and Emmitsburg to Route 15 which will take you to the campgrounds on the south side of Gettysburg. Both of those towns are small and since you wont have any turns to make it will be easy getting through them. Use caution going through Waynesboro. Pedestrians have the right of way in the crosswalk and this is one of those towns that regularly sends out plain clothed officers trying to nail motorists with big tickets.
If your staying on the West side of Gettysburg your routing may try to take you via the above Route 16 through Waynesboro and just short of Emmitsburg take you north via Jacks Mountain Road and Route 116. DO NOT take Jacks Mountain Road - there is an underpass of 10' 6" that you don't find out about until you are part way up the road. Stay on Route 16 about 1.5 miles past Jacks Mountain Road and turn left onto Route 116. That takes you into several campgrounds right off of 116.
If you are following I81 to Chambersburg and taking Route 30 East to Gettysburg (as some of the campgrounds west of Gettysburg will recommend) and your directions have you turning onto Herr Ridge Road to cut across from Route 30 to Route 116, there is a post at that intersection that makes that right turn very difficult. Keep going in towards Gettysburg about 2 miles and turn right onto Seminary Road. Much easier to negotiate that turn.
I would suggest you avoid taking your RV through downtown Gettysburg. Streets are narrow and the round-about at the square is stressful for normal passenger cars. I know the area well and wouldn't take my RV (similar size as yours) through the square.
2011 GMC Sierra Denali Dually
2012 Mobile Suites 40' fifth wheel
