Heated gear helps too. While the Powerlet plug has limited amps, it is convenient to use. I wear a Warm n Safe heated base layer shirt connected to the Powerlet plug. I then have some battery powered heated gloves to augment the heated grips and warm the top of hand exposed to wind.
Wind proof pant base layer and wind proof AeroStich shirt over heated base layer support the body. Wind proof balaclava helps neck and head.
With that setup, I’ve ridden my R18 Classic down to 20F.
My GSA has a proper pigtail, so I can use heated pants, socks and gloves, but the wind protection is closer to an R18TC than my Classic and I have Barkbusters blocking more wind at hands. I have ridden that down to 5F. It could go lower, but it’s rare to get below zero F where I live.
For me, both the R18 Classic and GSA are year round bikes. But as it gets below 20F, the GSA gets the nod. I don’t mind wet weather (rode my S1000R yesterday thru heavy rain at 60F after annual service), and I don’t mind cold. But I don’t combine them. Below 40F and wet, I don’t ride, black ice and bikes are a bad combo.