I'm busy 60% modding my 122 key terminal Model M and have ordered some of this copper tape with conductive adhesive to see how well it works:
http://www.adafruit.com/products/1128Hopefully I'll be able to solder wires to it and apply it directly to the membrane traces so I can hook up my Teensy. If it proves to not conduct well enough I'll probably fold over the ends to get better contact.
I've already cut up my membranes after drawing diagrams of the traces. I left extensions on them where the row and columns lines go which stick out past the edges of the cut plates and allow me to hook up crocodile clips or whatever for testing. Getting scancodes from my Teensy for all the ones I've tested so far, so it's looking good. I also put hammer and spring assemblies into all the barrels that have spots on the membrane so I can make them all generate scancodes and can support all kinds of layouts
Still deciding how to cut the case... I'm considering leaving the double F key row area for possibly adding some interesting gadgets to the board. But I do love the idea of making it really small, too...
I may end up making a new case for it from acrylic. Ho hum.. decisions, decisions.