Volume And Tone Knobs

Hey GMC's
On one of my guitars the tone and volume knobs move after you get to zero or ten.
If I turn the knob to zero and try to turn a little more the knob gets loose and the whole thing moves.
I tryed tightening it down but it didn't work.
How could I stop it from moving?

Help Me Pick Up Pickups

Hey all,
I will be getting a new guitar which is going to ba a Ibanez S470dxqm NF guitar. Pickup set up is H-S-H. It won't come with original Powersound crappy pickups it will have a Ibanez V7 on the Neck and V8 on the Bridge and HS3 (single coil) in the middle.
V7 seemes to have a good reviews but not the V8...I will wait untill I try the guitar to see what I need to change.
This guitar has a mahagony body. I haven't had this type of guitar body before and I don't know what type of pickup will sound good. I might change 1, 2 or all 3 pickups. (I know evrybody has different taste in sound) I just want you guys to share some experience with this.
I like to play all kinds of music mainly Rock and Heavy rock, and I have and Mashall AVT150 head through Marshall cabinet.
Any advise will be good.
Thanks!