Ron,
Your comments about wind are only partially correct. In 1983 I was called in to lead the planning for dealing with over 6000 acres of blowdown, so I learned a little about wind and trees.
The basics:
The most important factors in keeping trees upright are the strength of the wind, the density of the stand over the life of the trees and the soil conditions. Species is also important, but the importance of it varies.
Cedar is very wind firm, but often grows in risky areas. DF is also windfirm, but not as firm as cedar in those risky places. Yes, DF doesn't grow much of a tap root, but the experts say, and the physics say that a tap root isn't that big a deal in holding a tree against the wind. The importance of a strong tap root is a fallacy that is commonly accepted by foresters and others, so you are not alone. So you have a 20 inch tree, 90 ft. tall with a 12" diameter tap root. What's going to break first? The 12" tap root. How widely the root system spreads is actually more important than a tap root.
The most important factor is the density of the stand over the life of the tree. Trees grown in the open develop wind firmness and hold up better than those in a tight stand. Closely spaced trees will be at risk until thinning and for about 3-5 years after thinning. Look at individual trees growing in a pasture and you'll see the effect of being exposed all the tree's life. Ever drive thru the Columbia Gorge? The wind howls thru there. With all that frequent wind, strong wind, the trees have adapted to it over their life and rarely blow down or break off. The rule of thumb is that to maintain wind firmness, you need a ratio of diameter to height of greater than 1:100, i.e., more than 12" diameter for a 120 foot tree. That's just a rule of thumb and in my opinion, it's too optimistic, I would go for a larger diameter.
Those trees in a pasture also have large crowns, the "sail effect" you mention. Not important if the trees are adapted to the wind. Again, look at the Gorge.
I have heard the comment before about trees supporting each other in the wind. How do you suppose they do that? The strongest part of the wind either blows over the top of the stand or between the trees depending on density and what is upwind of the stand. When a gust hits a stand, they all bend the same way, in sequence as the wind strikes them. They don't support each other, and in fact if one leans against another, it puts more stress on the second tree, increasing the likelihood of that tree going down.
If wind is a concern, space the trees wide and thin often and gradually.