Do you details on that mod beyond the pictures? What's the X x Y matrix ?
key matrx is dead simple, rows and colums in the most simple matrix way. You can see on the right the row pins and on the left the colums (there were too many so it wraps around the teensy to the other side.
Took me a bit to figure out what you meant by XxY matrix. You can see in the pictures of the auction. 7*14 I think or count up the pins I've used on the teensy.
Anyway very simple mod, possible to do without any soldering, took me less than half an hour and most of that was deciding what layout I wanted in the soarer config file.
You just do the following: open the case (T6 and T8 required) remove the card reader, unplug cable from controller PCB, cut up cable and solder to teensy. Program and test. Reassemble KB. I believe I left the controller in place because why not.