I need and want a 120V roof AC unit on my well insulated 159WB. There are some install posts here and at Sprinter, but I'd like some ideas on choosing the unit and performance expectations. The 5000btu factory window unit on my 14' RV works great at my highest usage (95F, 80% RH. Typical Roof Airs are mostly 9,200 btu and 13,500 btu. Hein uses a 9.2 on his 170wb Sprinter and likes it. I see that car/truck factory cab units are about 14,000btu. For Coleman-Mach Mach 8 the 13.5K is 3 pounds heavier, costs about $100 more, and uses 1913 watts on full blast vs 1550 for the 9.2K. External dimensions are identical. So choosing one over the other for cost , size, or weight is moot. I want my unit to provide comfort anywhere in US at peak temps and RH. Some here say they just don't work, others say you can hang meat. The Mach 8 Ultra Low units have promise and are readily available. Any input appreciated.