The above post is spot on and much better conveys what I attempted to say earlier, that the spoilers cause increase bending moment. Thank you for the post and research. No one has mentioned this, but remember a number of years ago a Nimbus 4dm broke up over Minden, when it entered a spiral drive. Witnesses said the outboard wings departed the aircraft when the spoilers were opened. I know another pilot that left the sport when the spoilers on his ASW-20 opened at high speed. He almost lost control of the aircraft, and he did scare himself enough to stop flying. Spoilers on gliders are not dive brakes, and should not be used as such.