Admittedly I am no expert in this area, but I was tempted to start doing some math to enlighten our discussion. Instead I did a little google searching and may return to the math if I have time. Here are some personal observations and search results:
1. I have found pop ups to be more susceptible to flipping over particularly if the wind hits them from the side while they are setup. (It kind of looks like and acts like an airplane.)
2. Most equations include something about the coefficient of drag or something similar and our beloved
fiberglass trailers are about as good as it gets for this.
3. Most equations have to include something about center of gravity, tipping points, etc... Thankfully our trailers are relatively low to the ground and have a relatively low center of gravity.
4. It turns out semi tractor trailers have been studied a fair amount for tipping over and I think they would tip over before our units would. The University of Kansas said an unloaded trailer could tip over in just 20 mph cross winds (seemed low to me) while a loaded trailer could handle up to 60 mph. They looked at real world accidents and correlated it to nearby weather station data.
5. A study out of Canada related to semi tractor trailers concluded that travel in cross winds of 45mph "may be feasible" but becomes "risky" over 30mph.