LR,
good old fashioned balance tabs
That makes much more sense, but still, having to put tabs on a glider's ailerons indicates a pretty serious basic design flaw.
Reading the Flight article you posted, it looks like Slingsby were influenced too much by the HP-14 design. The Blanik's ailerons are much larger and the forces quite reasonable.
I was amazed to see the empty weight - 150lb more than a Blanik - and the correspondingly higher minimum sink speed - 48 kts compared to 39 kts. Also, the wing loading is 23% higher!
Politics aside, Slingsby and the ATC would have been much better served by license-built Blaniks. There are many L-13s still providing basic training all over the US and Canada.