Elevon travel is imited by end stops at a pivot link pair on top of the nose gear support. The end stops come in two flavours. The top ones are blocks made of Resocell, the bottom one is a round Resocell bar in a metal support structure.
A view through the service hole behind the pilots seat reveals the original version.
The end stops are shaped and positioned such as the deflection angles correspond exactly to the blueprints.