Calculating weight distribution.

You say your 29k empty with a 10' spread highboy. Assumtion: 20500# truck with an 8500# trailer.
Assuming you're 11500, 11800, 5700 empty axle weights.
You state 29' k/p to c-f/a + 5' to c/group = 34'1" = 409" w/b
You state 9' load, but no specific CoG, so we'll use 54" for center.
Expected gross (with 700lb fudge factor) 80700.
Target weights 12000, 33700, 35000. This provides a slight cushion.
Key target -> trailer Weight 35000-5700=29300 (tPw)

So the formula is:
CoG=(tPw*w/b)/PW
CoG=(29300*409)/51700
CoG=(11,983,700)/51700
Kingpin to CoG=231.8"
231.8" less 54", for half of the length of load is 177.8"
So measure 178" from the kingpin, and this is the exact spot you place the very front of the load.

 

Too much math!

Find trailer center, move center of heavier loads back as needed. If you goofed, avoid scales until you get rid of it.

 

Done that second option more than once.

 

If you pull the same trailer all the time, you only need to do it once at max legal weights.
Mark the trailer, it never changes.

Dad's used the formula for closed spread 5axles, all the way up to 13axles. It works every time.

You can't just do that with big trailers.