High speed flutter on a 3m glider

This was a lesson for me. 

I repaired the V-tail on my 3m BRISK glass sloper, after a bad landing, with a larger unit from an old and unused K2. The increased tail area caused the rear end to flutter during a high speed dive. The actual flutter was a side to side movement but the camera (progressive scan) recorded it up as a wobble; similar to the Venetian blind effect when filming through props. I stiffened the bppm and all was well until the glider was lost in a tip stall on a rubbish slope, captured on video.