This is what I could use to bring the front up to level. Not very clean, but gets the job done for now.
I opted for 1X4's since they are stronger that a sheet of plywood. Well, at least what I could find. I used only one floor support where the floor mats are and the rear of the slats rest on the cargo area notch.
This is the beast getting the rear underneath support installed. This joker is strong now.