How much difference does this really make when the winds are gusting over 60 or 70 kts?
Pilot DAR appears to have some realistic numbers. Unfortunately, the majority of muppets who tie lumps of concrete to their wings forget how much lift their wings actually produce and also how. I'll suggest that most small aircraft go flying with two people. That means the wings will have to produce at least this amount of lift in excess of their own weight (OK, mass then), so that's got to be at least 340 lbs. And what is the stall speed when empty? 35 - 40 kts. Admittedly, the AoA at this speed will be greater than it would be when parked on the ground but with 60 or 70 kts blowing it is quite likely the aircraft could become airborne even with 340 lbs hanging off the wing. So 700 lbs is a realistic number. However, far more effective would be spoilers strapped to the upper wings. They don't have to be very big (think about the effects of ice!) to do their job. Then all the tiedowns have to do is stop the aircraft from being blown about.
Tomahawk at Dundee. On its back and through a fence it would appear.
Best place for them. Horrible, nasty things.
PM