Maybe some will be interested in: I designed a Nylon link element for Gemini hooks. The normal version is the copy of the original link element, but made of laser sintered Nylon and on half price. They can be connected to each other, too. It’s advised to put them immediately before the end element, where less moment occurs when shooting.
The only problem is that there’s only one connecting surface between the two parts and when somebody is using too much force when holding the rifle, the parts can move. They are strong enough for normal use, but for ‘heavyweight’ users I designed a stronger one. This link has a fixed connection on the side where bigger moments occurs, this helps to keep its position.
Both versions can be bought here: Gemini Link.