Obi_1, Yes the K4 comes with a prepared space in the hilt and actually also a two button – card. This is why it was easy to add a button (if you remember, this summer when I was have doubt if I would go with the single button set up). The original card works as one button, despite having two buttons, but it could be prepared to allow for separated buttons. Instead of doing that I changed it for two small separate buttons.
SA22C, I will prepare some photos. I initially planned to glue it in place, i.e. to add glue and use the blade to make it perfectly centred, but the glue wasn’t strong enough. (I wasn’t brave enough to choose very strong glue.) As it works now, I separate the blade just enough to grab the plug. The wires are a little bit longer to allow for that. It’s not the perfect solution, but there are rooms for improvements. Be patient, I will provide photos within a few days.