HA HA, don't worry about the size !
They don't care, and actually, my little Becca rather enjoys running around with a foot long stick in her mouth !
But if you do go with a BStick, be sure that you watch close, and pick them up when they get short. Unfortunately, I am throwing about a dollar's worth of stick in the trash, when my two work them down.
Just be persistent about the "do not's", it just takes time for them to get the idea. Be patient !