yeah, i know you meant about gluing the wood, not the amp.
i guess i don't get why you are willing to destroy an interior panel with glue and holes, when you can make a couple small holes in the inner supports of the back wall (behind the carpet and plastic) and make a couple brackets to secure some wood.
mounting to the plastic, if it even held, would rattle like crazy. plus it just looks cheap.
got a pic of your setup as-is? may help the brainstorming. its been awhile since i've had an ex cab ranger (i had a 98 with a homemade box. 1 pioneer 12", 2 kicker 10", all in a forward facing box, divided and sealed, with a plexi top. the inside of the box was painted white, the back sides of the subs were painted with black light reacting paint, and i had 2 black lights in the upper corners of the cab.)
never took a pic because i had no computer or internet to share with. didn't need pics to show my friends, because they could see it in person.