My 2 cents;
Heavy loads at top, try to separate at least 1 space between other frames.
LCL loads with >40% circuit rating go next.
Sensitive and light loads near the bottom.
Goal Electrically is trying to keep the surges and stuff from flowing through the entire bus, along with having heavy loads closer to the subfeed terminations.
Goal Thermally is to put the heat generating frames where the heat can dissipate better and not transfer to other frames via conduction [hence the attempt to leave a space between frames or sections of frames, along with staggering them back to back].
Does this makes sense???
Scott S.E.T.