Fifth wheel placement on a long WB tractor

I’ve broken a lot of laws but never the law of physics.

 

Sounds like a good plan to me.

Only thing I would be concerned about is the difference in ride it might make.
Best ride should occur, (but not on all trucks), when the pivot point on the 5th wheel is centred between the tandems or load bearing points where suspension joins the frame.

You get a little too much weight ahead of the pivot on the 5th wheel and it will ride a bit rougher, slams the front of the truck when the tandems or trailer wheels hit a bump.
Too far forward can also cause steering problems in winter conditions, has a tendency to not want to pivot around the pin, particularly when the 5th plate is dry or the grease is near frozen, more so with short WB than long..
(most of them folks down south and mainstream Europeans can't fully comprehend Canadian winters)

Too far back during winter is not good either, but you know that already.
You need to find your happy place, sometimes it just takes a little fiddling around.
Hope you find your happy place before the snow fly's.

 

Even just a 100psi air gauge in the rear bags will help give you a reference point. You need to scale a lot at first and figure out where your redline is. For me 70 psi on the spread is 850 over and 60 is always fine so when im in the 65 psi zone i have the loader scooch something forward before i even throw a strap. My drives are always fine below 45psi. I figure i try to get a 40/60 reading with my hitch basically in the middle of its range for wiggle room to get the tractor axles legal. So far 48k and under i can always get legal with $20 of gauges.

Knoxville scale has segmented readout and is always on even when the coop is closed. I weighed myself there every time it was locked up for a few months just to correlate the PSI.

 

Longer the wheel base you will have trouble getting weight on the steer. On a KW 8 bag start with the pivot of fifth wheel over the back bag of the front drive. It's close and scale it and adjust it from there. If your talking trailer. If your talking quickswap good luck ever getting weight up there loaded.

 

I'd say still at or just ahead of the bag on the front drive axle is were I set anything unknown. Normally only need to adjust a few notches eitherway. However different loads, different kin pin depth. There is no one answer. But that should have you close.