I skim but have never traveled with one. I did however work for ZAP and helped box the boards for shipment. Go to home depot and get some high density foam cut thin strips (about 3" wide) and double them up on the nose and tail. On the rails put maybe an 8" strip on each side in the middle. Then run packing tape all the way around the rails twice. You can even put some big pieces of foam on the top and bottom. I've traveled with a surfboard (which is much more delicate than a skimboard) and all I did was put foam on the deck and bottom as well as put cardboard on the nose and tail. It was fine there and back.
What kind of board do you have?
2000 Ford Ranger 3.0L V6 4x2 XLT extended cab oxford white
3" Procomp Spindles
Fabtech 2.5" Kit
32"x11.5" BFG All Terrains, AR Sticks 5 wheels