Ottawan yes they are unstable in the high winds .I have had them blow over not to often but still not a good thing. I was useing half whiskey barrels but found them to be a hassle to handle on a hand truck when moving in and out of the garage. These pots seem to fit on the lip of truck much better. But your totally right. Perhaps i should have had the neighbor weld a metal plate on the hand truck when i used the barrels.I used to have to use a tie strap which was a hassle in early spring because our weather is unstable in spring and i would bring them in and out often especially when the night temps would really drop. Then when all danger of frost is gone i put them in yard.Perhaps one day i'll change them again.
Best to you
Martin