Quoting Nick-Danger, reply 8I've found the stack limit is 12 units (each unit can contain up to 12 individuals).
By stack limit, I mean the number of units that can sit in the same tile and move/fight together. IIRC it's 10 units. The current squad size limit is 12, but you could mod that higher pretty easily.
I mean that I can have a stack of 12 units that are grouped together as a stack. Anymore and the 'extras' are in a different stack, sitting in that same tile.
The 12-unit stack can enter into a battle I initiate.
My 'killer stack' that I use offensively is sov, wife, 4 kids, and 6 summoned rock critters = 12 units.
We're using the terms the same (well, you add 'squad' which is a unit), where we differ is you say 10 units per stack, when I have stacks with 12.
Test it and see 