I am getting this in console
Calling hook CanStackItem resulted in a conflict between the following plugins: CustomSkinsStacksFix - False (Boolean), StackSizeController (True (Boolean))
Calling hook CanStackItem resulted in a conflict
CustomSkinsStackFix is not compatible with StackSizeController. Your only option if you must use both, is to disable the weapon ammo dupe fix which essentially disables those hooks in the latest version.
Merged post
I found a viable alternative (i think) in the latest version which should make them compatible.
Calling hook OnItemSplit resulted in a conflict between the following plugins: StackSizeController - Item.ducttapex6.9407448 (Item), CustomSkinsStacksFix (Item.ducttapex6.9407449 (Item))