The desktop computer in my coach (see signature for particulars) does not have a wifi board installed in it. I have obtained a Netgear AC1200 High Gain WiFi USB Adapter that I plan on installing in on...
I would say you are in fine shape. There are lots of different ways of doing it but none are really any more or any less correct than the solution you picked, just different. Just note that with the Sleek it is important to have at least 6 feet between the cradle and the antenna. Also if you can get the antenna on the roof it will improve reception a lot, many RV's tend to be like a "cone of silence" for cell signals.