Hi Josey, I built the same shed in Maine two years ago. It's in an open location, windswept area. The frame hasn't budged at all and we've been hit with some strong winds. I think the roof sheathing helps hold everything together (we used 1x10 shiplap boards). The boards are perpendicular to the rafters so I don't see how the rafters could possibly "domino"; it seems like it would have to move as one. Also, the step-lap rafter seat is holding the rafter foot securing in place. Maybe you're over thinking this?
