Found this online today — a much more efficient weight system than the traditional cement filled PVC tubes. While I use steel bar weights, these have a smaller footprint and may be easier to transport in a smaller vehicle. Check out their website at happifeet.com. Be warned, though. They are pricey. HappiFeet are about $100 each, for the 32 pound style. They look quite efficient however, and can be purchased with optional levelers. For contrast, I paid about $75 each to have a fabricator make my weights out of 2.5″ steel bar stock. My weights are 75 pounds each though, 2 1/2″ x 30″, with a hanging loop at one end. They attach via heavy-duty tie-downs.
One thing is certain: an unweighted canopy is much more likely to blow away in windy conditions. The minimum weight you should have on each leg is 25 pounds. 40 or 50 is better, if you can manage to lift that much at a go.
[Note: I have two of the 45 pound HappiFeet. They hold down the center of my double, and work extremely well. Unfortunately, the company is no longer making them, as they were too expensive to produce and too expensive for artists to buy 5/3/2020]