I guess what I really want is a 3/4 cover.
My 'sadness' is that the half covers are designed to fit over the big trunk, so I hoped it would slide down over the bags instead since we have no trunk. I don't have a luggage rack so it just kind of grips the lip at the rear of the bike above the taillights. It's held on through pretty high wind, but also sags too much and pools rain water.