Well, we call 'dem tie downs "mobile home insurance policies". You can buy a set of four 3' screws (actually metal rods with a big auger at the bottom and an eye at the top) for about $6, and with some ratchet straps, you can secure the whole thing pretty quickly. I'd get a broomstick piece to slide in the eye of the screw to assist with getting it screwed in the ground effectively. When it's done right, I doubt the breeze will yank that sucker out. It stopped my truck when I left the trailer chain hooked to it once...

I carry two of these beasties in my trailer box to use when I'm out at regattas. I can recall beaching the thing after the RC calls the race when black clouds appear. Those help keep the boat (mast up) on the ground when others are tossing about (Florida T-storms can get nasty). Those ratchet-straps make quick work of tying the boat down...

And the other advice is certainly meritous - remove anything and everything possible - tramps, lines, mast, rudders, etc. If it doesn't come loose, it's certainly going to get whipped to death...

I'd be more concerned with the flying debris. Perhaps a road trip would be easier? Oh, and check to see if your insurance is up to date on that thing!