We just completed a 1500 mile roundtrip thru snow, sleet and rain with lots of blowing wind. In the past when I took the RV2 I was by myself and could fit it inside the Jeep (barely), but this time it was 2 Adults and 2 dogs plus the larger RV4. Buying a roof rack was an option but we really enjoy using the sunrider feature of the top, especially when we need to leave the dogs for a little bit and want to give them extra air. So I wound up with a Bestop Trail Rack instead for the extra storage for our Action Packers, and with the idea that I could combine a mounting point for the Oztent. With the Bestop Trail rack they provide a couple of eyelets, so I placed a Front Runner snatchit on each and then made a "guywire" to the upper handles of the tent. At the center of the tent I used another snatchit thru the spare tire, along with the steel "theft proof" cable running thru the spare tire and around the trail rack and back to the tent. I then ran a large ratchet strap from one end of the hitch rack thru the center handles and back down to the trail rack. At the bottom I ran one more strap from the hitch rack thru the lower tent handles. This gave me 3 side to side staps, and 3 straps to the rack and tire carrier, so 6 points of contact.
We never experienced any loose straps, or any side to side sway of the tent. This mount is sort of unconventional, but is similar to how many people transport skis in the winter. As for wind drag, our mileage was 14.8 doing 85 mph on the interstate going there, and 17.8 doing 65 mph and more backroads coming back. These number are very similar to tests I have done before with just Jeep wind drag, so I think the tent effect was negligible. The bag did get wet from snow and rain, but that would happen if it was mounted on a roof rack also.
If I was to do anything different, I might use a sling at the top handle to avoid potentially stressing the handles, but as they were just there to assist in side to side sway, I don't know that it would be necessary.