All the stock fairings combined don't weigh 20 lbs, it's probably around 10-12, if that.
And carbon fiber is typically half the weight of abs plastic, but that's ballpark, as there are variances in thickness across manufacturers.
If you want real cf fairings, cool, just don't expect a huge overall weight loss...just a huge price.
I did put a real cf front fender on the '18 Gsxr a few months ago, the abs plastic weighed 2 lbs, and the Moto-Composites cf weighed 1 lb.
My guess would be 5-6 lb weight loss max with cf fairings.
Maybe someone here can weigh their oem Gen2 fairings, and you can get weight specs from the manufacturer of the cf you want, and you may want to check with a few companies.
Magical Racing also makes/made cf Gen2 parts.
Let us know what you find out.