http://www.mycoolheli.com/450tipsandtricks.html
Read # 8 about the boom slippage solution.
I wish I took a picture of # 4 last night as I was building up a 450 CF for another student.

This is common on many 450 helis to have the boom slip. Adding the blade/sandpaper cuts adds some friction to hold it on.
grooves always go perpendicular to the movement you are trying to stop.