I had wing root fairings installed on my Nimbus 3 around 1991
by Tracey Tabart (Aussie) at his Turf Soaring shop (AZ). I
believe he got the fairings from Schempp-Hirth.

wrote:
The Ventus A and B models really need a good wing root fairing.
Schempp-Hirth realized their mistake years ago, and offered a simple
aftermarket fiberglass fairing mod kit. I installed mine during the
early 80s, and it really helped the low speed performance.
I think it may still be possible to obtain a similar fairing, and
possibly Al McDonald or someone else knows where?
Dick Johnson