Which Minecraft versions does StackSize support?
Restricts the stack sizes of all items in a player's inventory based on permissions.
CurseForgemod
No published Minecraft release
StackSize has not published for any Minecraft release we can read.
One mod is never the whole story
A modpack can only move to a new Minecraft version when every mod in it has. McPackSmith reads your whole pack and tells you which ones have not caught up - and StackSize is only one of them.