there are svereral parts with your katana 2, and depending on the socket, you just assemble one of it. for so775 you have to assemble the push-pin-"part", you can see it here
http://www.scythe-eu.com/en/products.../katana-2.html on the right bottom, the part with the black things on it.
but you have to use that part, I don't know another way. And in ordner to use the retention kit, you have to use the so478-part, which you see just left to the so775-pushpin-part. so the universal ret. kit will only hep, if you still got that part.
But if you are from germany: I assembled my katana2 with the universal ret. kit, and so I do not need the so775-pushpin-part any longer. maybe I could send it to you, if you pay me a little bit for it? but I don't know, if this is worth it...
maybe even scythe can send you the part, I don't know...