John Galloway schrieb:

The manual says the give a glide angle of 6.7:1 (which
fits with my measurements of 800fpm descent rate) at
approach speed

Very interesting, indeed:

JAR 22.75 Descent, approach
It must be shown that the sailplane has a glide
slope not flatter than one in seven at a speed of
1·3 VS0 with air brakes extended at maximum
weight.