I haven't seen that one, but it sounds scary. Maybe you can get a neighbor to try one first
. The tip on driving habits is spot on. My 08 4.6 has gotten as high as 20+ for local driving and 25 on the highway. But this means keeping it at 63 or below on the highway, and doing as much coasting as possible locally. It is kinda fun to see what you can actually do with this truck, but sometimes in traffic you just have to get on it to enter highways and to avoid problems.
Be advised, I live in southern Louisiana and the only things resembling hills are the bridges. Pretty much flat down here.