We bring with us 8 75 pound bags of sand (600 lbs) and put two on the corners of each legs with the ratchet strap down looped around the bags up to the corner. We also keep a truck on site and strap two legs down to two of the tires. If the wind kicks up we move the coolers to the center and use some long bunges to stabilize the middle of the tent.
If a storm rolls through we will quickly drop the top down so that the canopy is still up but it's not extended (think total height of about 4 feet) and retighten all the straps. We've rode out some pretty serious storms and survived watching other popups twisted, crushed and flown away. So that has worked for us pretty well. And by serious storms I mean tornado siren serious.
Neil -- "Easy Bake Master"
NB Bandera [gone to heaven...conveniently located in Long Island, NY]
Rebel 23, WSM A, WSM B, UDS, Easy Bake Oven
Pork Pistols BBQ
MOINK...It's what's for linner.