It seems as though I face a dire problem here.

While playing at gig/practice volume, my cab seems to vibrate my head enough that it starts to slide off the top of it.

What should I do to stop this?
Im trying to avoid taking the bass out because I enjoy my tone currently.
Jackson DK2M
ESP LTD Viper-400
Jackson RR3
Gibson SG Voodoo
Washburn Acoustic

Peavey 6505 head.
Marshall JCM200 TSL100 head.
Vader 4x12.

Maxon OD9.
Boss NS-2.
Set the head on the floor, or Velcro it to the top of the amp.
Quote by woodenbandman
My dear man, I must petition you for photographic evidence, or the described events cannot be verified, and will be written off as fallacy.
Duct tape perhaps.

EDIT: Just set a big rock on top of the head.
ESP LTD EC-256 and a Fender Deluxe VM
Don't put your head on the cab.
Jackson RR5 Rhoads
ESP Viper 400
Epiphone Les Paul EMGs (81/85)
Edwards E-CY-165CTM
FJA Modded ENGL Powerball Halfstack
Framus Cobra + Avatar 4x12 Greenbacks
If the head has little rubber feet at the bottom, you can make something like sockets in the top of the cabinet for them to stand in.