I have 2 x 12" Alpine type S subs in a enclosed box. I'm not sure how much it weights, and maybe it's jsut the type of carpet used on the box but I have never had a problem with it moving.

 

if you position the box right you can easily bolt it in with metal brackets to the upper deck structures without any problem. there is a U tube of metal that runs along right behind the rear seats, and then one that runs right along where the rear window meats the metal. I bolted up into those sections. You can also bolt down through the trunk floor in most places near the spare, but be careful where you choose to drill and so forth there. I used 3 metal brackets and it seems to be a pretty good solution for me.

 

Heh, mine dont slide either. Could be the weight. each sub is 25 lbs and the box is another 25 lbs coming to 75 lbs, and no movement.

 

I have an assload of movement my subs way 85 lbs. I have 2 12' HE2 and a Qlogic box.

 

screws...or brackets... shouldnt move an inch... damn some of yall boxes/subs weigh 100 lbs! thats crazy... as for the spare tire... if you have the box sittin up more u should IMO have plenty of room to lift the carpet up to get to the spare tire... maybe not lift it up all the way so it might b a little more of a ***** gettin that spare out... but how often do u put the spare tire on anyways??