width of space in back of denali xl

[Highs On Bass]

I'm going to be picking up a 2011 denali xl 1500 in a few days, in decent shape, I'm planning to put a smaller system *(bigger than what most would consider) but small to me, I have never owned one of these, does anyone know how wide of a space between the interior plastics i have?
plan is to remove the 3rd row seating, and place sub box there. I just don't know how wide that space is just yet. anyone got any ideas of measurements between plastics I would have to work with?

 

[B-train]

I believe it's around 48 inches or so. You should be able to fit a piece of plywood in the back of an XL no problem

 

[Geotrash]

I believe it's around 48 inches or so. You should be able to fit a piece of plywood in the back of an XL no problem

Confirmed. A hair over 48" in width. Can fit a sheet of plywood in it and still close the tailgate with the 3rd row of seats removed.