We did 301 the other way on our way back from Hatteras this year. Easy ride. The bridge on the Potomac was a little scary.
Also consider Rt 15 south out of Harrisburg. We took this to Fredricksburg VA from Stroudsburg PA on our way to Hatteras. A bit longer but worth the extra for the views. This way also bypasses Balmer and DC.
SubVet is correct about the Norfolk tunnels. Before the tunnels, you just pull into a weigh station type area and the nice VA trooper verifies that your propane is turned off.
Jerry & Jeanne
1996 Safari Sahara 3530 - 'White Tiger'
CAT 3126/Allison 6 speed/Magnum Chassis
2014 Equinox AWD / Blue Ox