tying longboard to Jeep Cherokee factory rack; advice?

[Guest]

Hi, I'm road tripping with my longboard for the first time. I'll tie it to my 1997 Jeep Cherokee's factory rack. This is my plan, pls. advise if it looks like I'm missing something:

-- rac roll pads on the crossbars
-- crossbars spaced as far apart as they will go
-- 8'2" longboard goes on, fins forward
-- first I'll tighten the built-in straps included with the rac roll pads
-- next I'll take a 21-foot super-duty polypropylene strap with cam lock and "harness" the board by first looping around crossbar (behind fins) in front, crossing length of board diagonally over top; looping around crossbar in back; crossing length of board diagonally underneath; then joining and tightening strap at crossbar in front.

I'll be highway driving @ 65-70mph for a couple of hours so I want to be sure this setup is stable. I have some concerns re: do I need some sort of rubber no-slip padding where straps contact the board?

Any suggestions are greatly appreciated. Thank you for reading.