I managed to do a test flag at work today for the Savant Zombies.
However, the flag pole is rather short, this is something I have noticed on some of my other models too.
When I painted up the ghouls I extended their flag pole to take the flag.

I had done a smaller flag as I wasn’t sure of the required dimensions. As can be seen here this is about as big as you can go to fit the pole.
I will redo this flag either as a pennant or a rectangular guidon.