Just bought a new Keystone Cougar! What else do I need?

I'm as proud an owner as you will find for the EB F150. I've made 4 cross country trips with my 6500 pound loaded travel trailer and family. It did an incredible job in all areas except for the one you've already mentioned. On long descents in the mountains, you will need to drive very smartly. I was a little worried of braking on a few occasions with my lesser weight. Like you said, its what you have now, so it will work. In Oklahoma, you will feel like you have plenty of truck. Not so on downhills.