Trandg; I've updated the design to have longer legs, so the extensions become redundant. Insertion into the skids appears to create a stronger bind than into the extensions. I have a prototype that I'm not yet willing to sell that is clip on, rather than through friction.
Shapeways has begun promoting the redesigned legs, and I've reduced the price by more than 25% to encourage sales.
Hopefully at $59 for the full kit this will be more enticing for some of you.