Fer-Tak-Er I use #9 wire. It fits snug with the wammy's.
What type of whammy are you using?
I use a 3/32 double ferrule for a whammy on my 5/64th coyote and wolf snares. This ferrule fits well on the 11ga wire. I often think people are confusing the 11ga wire for 9ga but I could be wrong. The 11 ga works very well for me.