I bought a Flyscreen after 17k without a screen, and have to say that it takes a lot more wind off my head and torso than I expected it to. Most of my riding is in excess of 70 mph, and I still would not consider the need for a bigger windscreen any kind of priority.
It does make for a little more windnoise, no buffeting of the head, just noise as the air rushes over the top of my visor (full-face SHOEI RF-1000), so I wear earplugs for that now, and probably should have worn them before.
Better looking and less conspicuous than a larger shield, too.
Works for me.
