You're loaded heavy with 1/2 tank of fuel onboard. Using the following numbers, where should you move the 5th wheel to get it setup properly?
steer axle: 10,800 pounds
drive axles: 34,700 pounds
Weight transfer: 500 pounds per hole.

The best way to make sure the 5th wheel is set properly is to scale the truck with a minimum of 1/2 tank of fuel and a very heavy load. Under those circumstances, you will want the 5th wheel positioned so that the steer tires are as close to 12,000 pounds as possible without going over, and the trailer tandems as close to 34,000 as possible without going over.