I hate math....

first, slide your tandem's all the way to the front of the trailer. this should simplify by making the trailer axels the higher weight. scale. now look at your ticket, cell phones have calculators so it's really very simple. you of course have three weights on your ticket. steer axels, drive axels, trailer axels. since you slid you tandems all the forward then your trailer weight should be the higher weight. subtract your lesser weight from your higher weight. divide that number by two. now divide that number by 225. what ever that final number is, slide your tandems back that number.
example.
11,640 steers
32,460 drives
34,840 trailer
34,840 - 32,460 = 2,380
2,380 divided by 2 = 1,190
1,190 divided by 225 = 5.28
slide your tandems 5 holes towards the back of the trailer.
I have reweighed many times to double check this system and it has been correct every time, in fact it has been within a couple hundred pounds of being an even distribution of weight. 34,840 - 1,190 = 33,650
32,460 + 1,190 = 33,650 these numbers I used here were random numbers I made up but you should get the idea, once you have done it a few times it will second nature, as a matter of fact I have not done a reweigh in 4 or 5 years and have never had a problem, in fact usually get a green light on prepass.
hope this can be some help
b

 

perhaps the frustration is whats getting in the way.

tandems forward - toward the cab adds weight the further away fron the cab the tandems are adds weight to the drives

 

Sealed trailers pose a problem, as you cant see how the trailer was loaded and how far back the product is.
Most times most weight will be on the drives since there is always product up front.
I run my fifth wheel all the way forward, tandems all the way forward, weigh the truck and figure 250-300 per hole.
Always or usually have 1000 pounds to spare somewhere, so if you need 1000 moved,move 4 holes, there is a buffer there.
I rarely need to reweigh unless Im totally at gross.