Can you still put the third row seats up with the back one on?
You'd have to remove it or fold it back.
Love weathertech's, have had them in every car I've owned for the past 15 years or so. My explorer came with the factory slush mats as a dealer option, they are ok, but I would rather have the weathertechs. I keep mine in all year round, carpet gets dirty so easily and my OCD requires me to wipe these down weekly.
For the cargo area, those of you guys who go to Costco they have a "universal" cargo mat made by weathertech, I paid 29 shipped for it, but if they have it in store which I believe they usually do it's even cheaper. Fits pretty close to perfect, obviously not as nice as the one made for the car, but it's quite a bit less expensive, just a tip for those looking for a cargo mat on the cheap.