The measurement from the tailgate to the drop off to the trans hump is 48" so that was the width of the plywood and 42" wide at the tailgate, the front is 48".
I had 23 months and didn't order a thing until I got the call that it was in at the dealership. I wasn't in any hurry and have an awesome other ride, my 700rwhp 2018 F150 that kept me busy for several years...lol