5th wheel wire harness

Just bought a new 5th wheel for the family- Keystone Mountaineer 345QBS.
Anyway, I am getting ready to install a hitch in my truck. The truck is new so drilling additional holes in the bed makes me a little quesy. The dealer told me that alot of people just drape the wire harness from the fifth wheel over the tailgate down to the factory plug. How many of you recommend biting the bullet and installing the additional plug in the bed of the truck. I have concerns that over time the wire harness drapped over the tailgate may beat it up. Thanks for the input.