What are people flying at these days with the 10mm extension? the 1st or 2nd hole?

What is a 10mm extension?

The most I or the Heli can handle is probably the 3rd hole up. Just adjust it to your own flying needs. I was flying on the 3rd but tunned it down to the 2nd hole for more indoor control.

I have the elevator (? forward/ backward ) servo on the 3rd hole and the slide left/right (?) on the first. But I'm still really new. I need the elevator on the 3rd to keep me out of trouble ( read walls/ trees/ cars/ cat/ wife ) but am still for the most part hovering arround, or the left/ right is rarely used by me ( for now...... )

The third hole or how it came stock is good enough for my CX2. Be more aggressive if you have a Blade 400 or better.