I think that no matter which truck or camper you have that securing the camper boils down like this:
1) you don't want fore-and-aft movement when underway so they need to be installed at angles that prevent that
2) you don't really want any side-to-side movement so if you have any angle on the camper-to-bed fittings that is a good thihg
3) you don't really want any up/down movement when you go over rough highways or terrain
With this in mind, I believe that any of the methods discussed above to prevent any LOOSENING of your tie-downs (whatever you use) is paramount. That will prevent all three of the above considerations.
However, as has been discussed in other threads, it is equally important to beef-up the eyebolt attachments in the camper with the addition of a gusset plate inside the unit and outside so the eyebolt is prevented from tilting in any direction. I also believe that SOME tension on each attachment to the camper is needed....not so much it tears the camper eyebolt attachment out, but enough to prevent it from any movement.
I believe that inertia is the enemy here....a loose attachment will allow the camper to move and the force on the eyebolt attachment is MUCH greater when it stops that movement than is incurred with a stationary eyebolt attachment.
So, using any type of lock-nut or jam nut to prevent the loosening of the tie-down (turnbuckle or what ever) is a step in the right direction. Securing each corner just past SNUG to TIGHT but not enough to put a strain on each corner is preferable. How you arrive at what "too tight" is as opposed to just "tight" is up to you....but don't pull the eyebolt out of the camper or start to tear the camper bed if the attaching point in the bed is not beefy enough.
