For me 2 shims on each side made quite a difference. The heli went from a loose feeling in hover to quite tight. I'd say definitally worth the $2

They go between the o-ring and the stepped metal washer against the inside BB on the blade grip.

I also lubed up all moving parts with 30 weight RC Car Shock Oil. It's pure silicon oil and works amazing.

I'm using the 2bb grips as well. My heli is smooth as silk.