The critical, but often neglected aspect of keeping a ship on the
ground, undamaged is to reduce the angle of attack, both while tied
down and during ground handling. This dramatically reduced the load
on the tiedowns, as was very well documented in the old Red Schweizer
Soaring manual.

As a working example, Skylark North in Tehachapi (and formerly the
brutally windy CalCity) has never lost a tied down ship in 40+ years
(and only 1 while being ground handled) in a very windy environment
using this technique. Caracole in CalCity keeps their fleet safe
using this method as well.

Short of a tornado or similar extreme event, properly tied down ships
should never be lost. Of course, "never" is a very long time

Creating adequate tiedowns in a landout or safari situation is
problematic but getting the AOA down is not that hard (flaps full
negative, constrained tail dolly, inverted wash buckets, wood, or a
mound of dirt for tailwheel and dig hole for main gear).

I believe the best "combat" landout mode for keeping a glider on the
ground in high winds is to orient the glider 90 degrees to the wind
and expend all resources on keeping the upwind wing on the ground. I
have seen it used to good effect in extreme wave/rotor conditions
using a tractor tire, tiedown kit, rocks, and the pilot's body.