[BAracer]

The 40/60 weight balance thing has been around for probably decades. I don't follow it closely, but it isn't a bad place to start with weight tuning.
I am fortunate in having my own 65 foot track for depth testing, and race weekly around a group of 6 or so wood tracks in all, so I get plenty of opportunities to experiment.
As the guys in the basic tuning thread mentioned - it is more like a multi-way split of different things to experiment with, rather than a linear process.
But if the car is sidewinder OR angle-winder, I always begin my weighting process with a few grams to hold down the nose, as the car is probably 30/70 or thereabouts.

I guess I first make sure it is flat/square, 4 wheels on track, guide full depth, all wheels glued and trued.
As I begin to drive I am looking for undesirable behaviour - eg a saloon, or even sport GT like this which rolls over, it needs low weight.
If it deslots without rolling over, I am asking myself, which end, and how?
If it lifts the nose out of the slot when starting, or coming out of tight turns, I am checking the braid is set as low and flat as possible, then weighting the nose or tail as required
For podded cars, I am checking the amount of pod float is even all around, and that nothing is catching, and asking myself if the pod might be flexing, - motor screws help with that, as they turn the motor into a stiffening element.

If the body is heavy, I am asking whether I want weight in the pod itself, or on the main chassis plate, to make the whole thing more stable under cornering load (and sometimes I end up with more pod weight, other times sod's law comes into play and I add more to the chassis and have quite a light pod and drive-train.

If it sounds or feels tight, or seems a little unpredictable - I am really looking at possible chassis/body interferences, chassis/pod interferences; or of wheels inside the arch touching the body during corners.......

Sometimes think I am a top 1% tuner, and other days I think I am an utterly useless plonker when I cannot sort a behaviour issue on a car.

Further thoughts on the topic from Slotloco in his Review of the Scaleauto 991 R-Series car...