Figure out the size of your pet when it is double shrink by typing:
/echo ${Me.Pet.Size}
Make downshit:
/if (${Me.Pet.Size}>##) /casting "Tiny Campanion" gem#
Size you want
Spell name or item name
"gem"+ number or "item"
same for buff:
/if (${Me.Pet.Buff[Necrotic Cyst]}) /casting "Spell/Name" gem#