The number to start with is 18 by 20 — that's the string pattern on Sabalenka's Wilson Blade 98 v9, and it's probably the single spec doing the most work in her game.
Soft is not the same as arm-friendly. The cheapest, mushiest multifilament on the wall at your local shop will feel like a pillow on day one and a hammer on day twelve, because once a multi…