I think one of the best replies was tracking with the oft hand. Not that it works 100%, because you need to actually swing at the ball some time, but it allows you to track the ball until it's descending at least
Ideal safe overhead technique IS high oft hand, like a toss hand on the serve. So why not block the sun with your oft hand?
Maybe because at times, you spend so much vision blocking the sun, you lose track of the ball.
And just as you swing, while the ball is 15' high and descending, you lose the ball in the sun at the critical moment.