I'm building David Johnson's danish cord bench (featured in Fine Woodworking in 2020). I am building it out of ash. Rather than traditional mortise-and-tenon joinery as David uses, I'm going with the domino.
The stool features one front/back rail, and then a pair of side rails because of how the danish cord is wrapped around them.
My question comes in grain direction for creating the strongest joint / stool. I have two options on how I orient the grain on the top side rails. Should the grain run the same direction as the domino mortise, or should it run perpendicular to the mortise?
I have mocked it up with some pine, but am building the finished project with ash. As you can see from the design, that top side rail will have stress in two directions -- pulled in toward the center of the stool just from the pressure of the cord, and then pushed downward when the stool is being used.
So what makes the strongest stool - grain running parallel to the width of the mortise or perpendicular?

Stool1.jpg
Stool2.jpg
Stool3.jpg

On that top side rail - should I run the grain parallel to the mortise, like this (OPTION A):
Stool4.jpg

Or should I run the grain perpendicular to the mortise, like this (OPTION B):
Stool5.jpg