1999 Silverado back seat question

[Fifty150]

I have 99 Silverado 3 door, I would like to install a small sub enclosure underneath the back seat. The box fits but I need another 1/2" of space between the top of the enclosure and the bottom of the seat. I would like to use spacers to raise the seat brackets, I'm pretty sure that will work ok, my question here is about the backrest of the seat itself, I know it moves when raising the seat bottom, is it attached to the back wall of the cab in any way? If so, is there enough leeway to accommodate a 1/2" raise in height? 

[Ak_grown]

there are hooks on the back of the rear bench seat, we would add spacers to raise the seat for a sub box, but trim the hooks that secure the seat to the back wall. the rear seat would just be able to fold down after trimming the hooks. if you don't like that you could find a way to extend the hooks so the back will not fold down. 

[Fifty150]

So if I only raise it 1/2" the hook will come out of the loop on the back wall of the truck?