I have been running my 40 for 20+ years no top. I recently put a roof skin on the back half and it made a significant difference in the noise. Truck is quiet now, you can not hear any gear noise, only the exhaust & tires, thrilled. I was doing it as a support for my roof bag but it has quieted the truck to the point I can have a conversation on the freeway. And it shades the fridge.
