Yep, I agree it is not related to DBB or any mod set. Thanks for the confirmation though. It is definitely a game mechanic.
I question the game mechanic though if it is actually working correctly - eg please see my post in the main thread. It appears to be multiplying consumption by 30X.
Now, if this is the way the designers intended, no problem - but it does seem a little unusual that in the example posted in my other thread you will see a very small (1,200 man) overstack on the atoll causing the supply consumption to immediately jump 30X plus the additional %overstack. I've run the numbers now in about 5 test cases set up in a small scenario and get the same magnitude of result repeatedly.
And yes, I do like it being more difficult and I believe it to be realistic to require more supplies for the overstack; but I think there is a mis-calc somewhere.
Perhaps I misunderstand, but in your other thread you wrote (boldface emphasis mine):
I just set up a small scenario and created an overstack on an island - in this case Fukue-Jima, stacking limit of 25,000 troops under DaBabes Scen 28 C with stacking limits.
In this case, for grins I placed 5 US late war divisions - ~71,000 troops; set the airfield to lvl 6 and the port to lvl 3 and placed 90,000 supplies on the hex.
Just an FYI - the units consumed 26,000 supplies/day or right at 30X their ordinary daily consumption for this overstack. Seems somewhat extreme, but, so others don't get caught by surprise the effect of overstack is dramatic. Fail to pay attention at your own risk.
That makes stacking of 284%, which is over stacking of 184%, or 46,000 troops above the 25,000 stacking limit. Where are you getting that "...very small (1,200 man) overstack on the atoll causing the supply consumption to immediately jump 30X plus the additional %overstack." example from? In your other thread I see a huge over stack of 46,000 surplus over a limit of 25,000, not a "very small (1,200 man) overstack".