I drilled holes in the side of the Empeg mounting cage and then used some shallow/tapered bolts to secure the cage to the modified dash kit. I also used the ISO mounting strap to secure the back of the empeg cage to the back of my Alpine unit. Let's just say it is very secure

I would love to pull it out and take some pictures, but it is extremely tight behind the units (wire city) and it's a good two person job just to get the units back into the dash.......