Suggestions to Secure a Sub Box
 

Ok I am installing some sub in the back of my 05 M3 Hatch...

I was thinking about securing them down some how, so that they could not be easily taken out of the car. You know for those people that think they can just take whatever they want from whoever has it...

I was thinking about bolting it through the box to the floor, but with the cargo tray there and the spare tire that might not be the best of ideas... Plus the fact that that part of the floor can just be lifted up and taken out...

Let me know if anyone has secured a box before and how you did it? Any opinions or suggestions are greatly appreciated!