I always like to pitch tarps below treeline. I have a cat-cut tarp of comparable size to the Grace Solo and I'd say that it's workable above treeline, even in high winds. However, in high wind, when it starts raining, the rain comes down sideways. Meaning that you'll be pitching that tarp in a very low, stormworthy configuration. With the Grace Solo, you can easily do this, but wiggle room decreases to coffin-like accomodations in this type of pitch. The reason I like to have trees above me is because when the rain hits the tree branches and leaves, it stops falling sideways, and instead falls mostly straight down, thus allowing for a higher, more ventilated pitch of my tarp. So what I'm getting at is that perhaps a larger tarp, or even a shaped tarp, would serve as a more comfortable shelter above treeline.
I think if you were intent on using a Grace Solo above treeline, this would be a situation where an eVENT bivy would be a necessary precaution against wind-driven rain for the times when you don't want to pitch the edges of the tarp all the way to the ground