I'm trying to figure out the best mounting layout for installing 20x16 sail shade over my patio. My plan is to anchor 2 corners to roof rafters, and 2 other to trees. I'm worried about load from winds, and how would all of this hold up to that. Mostly my concern is that trees would be flexing in the wind. I'm planning to anchor at ~10' off the ground to a 10-15" diameter tree. I don't like to use posts (that would not have this problem) since they would end up in the middle of the grass. The trees are ~35' from the corner of the shade. To install post by the tree, I'd need to bury it 5' deep (for 10' above grade), which would be quite a fit.
So 3 questions I'm trying to address:
How should I go about calculating loads I should be expecting, and what kind of load can my roof take before damage occurs?
As an idea to solving roof damage, would you recommend using some sort of fail-safe mechanism that would break and drop the shade in case winds are too strong before doing damage to a roof? If so, what would that mechanism be, and how to properly size it?
Is there a way to estimate tree trunk flex in strong winds, other than observing when such an event occurs?