I would not trust my glider to those things. A better solution is (in
the glider) a couple of sleeping bag stuff sacks. After landing you can
fill them with rocks, dirt or whatever you can find that is heavy. In
the trailer: two 18-24 inch lengths of 2" steel angle with 45 degree
points on one end and half inch holes at the other, plus a sledge
hammer. Drive those puppies into firm ground at a 45 & it will take a
tornado to pull them out (removing them is relatively easy by hitting
them sideways).

Tom