defjr, to answer your question personally: Yes, I have planned stuff. Those plans rarely survive contact with reality. Dad used to say for every jug of paste, there's a pair of scissors....and more paste
The only thing *I* stress on is doing something irreversible to something on the outer layer that can't be covered with trim. "Trim'll cover it" (one of my father in law's favorite expressions) only works on the edges!
It's all a pretty inexact science so long as you don't put all the batteries and water tanks behind the axle or make the tongue out of luan. Lots of people tend to over-think it all, and are paralyzed by not being able to achieve absolute precision. Think about it: Jack Spratt and his wife riding somewhere together, there's a heck of an imbalance side-to-side....but in the real world, cars don't flip over with a hippo and a string bean riding together. For that matter, flying solo (no passengers) has the weight shifted 200# to the left

Front-to-back, an empty pickup and one loaded "safely" to its limit have WAY different handling, but neither is demonstrably worse than the other. The hard-stops for me are overloading a spindle/hub or a tire. That is the weakest link, and it's also damn near impossible to do without it being glaringly obvious.
Point I'm making is, there is an ideal distribution that we all strive for, but it's such a wide window for "acceptable" that just being conscious of what "ideal" is, will get you to where you can be happy with your outcome!