Normally a non-slider 5th. wheel on a single drive tractor is set up with the trailer kingpin just slightly ahead of the centerline of the rear axle, so some of the trailer weight goes onto the steer axle. Ths sliding 5th. wheels we used on the twin screw rigs I used to drive were positioned so we could add or remove weight from the steer axle to get legal on a heavy load. The steer axle on a 5-axle rig can carry a legal maximum of 12K lbs. with an 80K gross weight.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!