Do the floor and wheel wells as well. You'll be happy you didWe just bought a 2020 4x4 and are planning a trip out West for September -- Grand Canyon and Bears Ears, hopefully -- in our as-yet unconverted van. Yesterday was the first baby step of modification = installing some Noico in the van walls.
While the factory plywood floor was up, why not? Does it help? I'd have to do before-and-after experiments to see, but that seemed way too much like work. That is, I'd have to do (1) noise measurements as bought, (2) add insulation only (as Hein recommends), then do noise measurements, and (3) take floor out again, and insulation as well, add Noico, put insulation and floor back, then do more noise measurements. I'm not that dedicated to the pursuit of knowledge.Noico the floor as well?