This may be a bit late, and if you use knots and it’s been successful I’m happy to hear it. That said I sail and keep my boat moored on Lake Geneva. I’m sure some boat owners use knots, but I don’t know of any. I use thimble and eye splices. Knots lower the breaking strength of the line they are in (up to 50%) and can come undone. Splices minimally reduce the strength of a line and if done correctly can’t come undone. We have a lot invested in our sailplanes and our tie down equipment should be sized for length and strength for each sailplane. I’m willing to help with this if help is needed when I’m back in town.