Having destructive weather at a NSS Convention should not be a surprise. I've been to 19 conventions. At 5, there were high winds, heavy rains, and significant destruction. That is about one in every four conventions. It is also about 4% of the number of days most people stay at a convention. If you look at this map (
http://www.nssl.noaa.gov/hazard/hazardmap.html), you will see that we are getting thunderstorms at the normal rate.
In every wind event, many of the sunshades get destroyed and just about all get blown down. About the only sunshades that don't get destroyed when they get knocked down are those made from blue tarps. They generally fall down and wad-up in the slightest wind. I personally don't think that anybody should bring a sunshade to the convention. They will inevitably be destroyed and will have to be thrown in the non-recyclable trash.
I made and ad-hoc study of the tents that survived the windstorm at the convention in Sault Ste Marie, Michigan (1987). The campground site was a plateau. Almost the entire site was exposed to any potential winds. The thunderstorm that hit the site caused a lot of destruction. It blew some tents and sunscreens into the woods around the campsite; some items were never found. I estimated that 90% of the tents were collapsed or blown over. Mountain bivouac tents collapsed. Dome tents collapsed. Family tents collapsed. The tents that consistently survived were only of two types: tightly pitched pup tents or tents with both longitudinal and crossed poles.
I had a pup tent not because I was then experienced with the survivability of tents, but because I was cheap. I had purchased it for $3. I did the right thing for the wrong reason.
When it came time to replace my pup tent, I purchased a Sierra Designs Lookout CD. My Sierra Designs Lookout CD did not collapse at the convention in Marengo nor in any other storm event. There may be similar designs with crossed poles offered by competing brands. You can empirically tell whether a pitched tent will withstand wind. Just lean against the side; it it collapses easily it will easily collapse in a storm. Perhaps you should purchase a similar tent before the next convention and do the right thing for the right reason.
Besides wind, there is also water runoff that causes damage. If you pitch your tent in a drainage swale, water will enter your tent and damage your stuff. At Marengo, I observed from 3-inches to over 1-foot of water flowing through some of the tents. These cavers either didn't observer their surroundings or allowed others to pick their tent sites for them.
Good campsites are not easy to come by at most convention sites. In Sault Ste Marie, most of the site was exposed to the wind. That is the reason for the widespread destruction in that convention. At Marengo, the 60 acre site had perhaps 15 acres with good drainage and maybe 2 acres with both good drainage and limited wind exposure. There are similar issues at every NSS Convention campsite.
Good tent sites are also artificially scarce at most conventions because "Sooners" mark out 1/4 acre or more for their friends or casual acquaintances. I don't think that it should be allowed, but I doubt that anybody has the balls or authority to stop the practice. Frankly, if you want a good tent site at convention, you have to rebel against this rude, self-centered behavior by pitching your tent in the best site for you. Be assertive, but be friendly too. It has always worked for me; it should work for you too.