Pictures appear after their descriptions.
Here are the key switches, or buttons as I called them in the previous installment. Drilling the top one was the activity that tore the PCB. Note the thin PCB? That's the trackpad controller board from the EzTablet.
Here is a wider angle of the repair jumpers after both ends were soldered.
This next shot helps you understand where the trackpad USB controller board was installed in relation to the other components. Those wires that go up past the top of this pic are connected to a pencil-thin PCB which was removed from the EzTablet keyboard.
Next you see the USB controller board in all its glory. The wires on the left go to a USB cable that leaves the keyboard through a hole, and the wires at the right-ish top go to the trackpad. You can also see the point-to-point wiring on the key switches.
Writing R W G B on the PCB let me recall the colors of the wire order in the socket. Since I lost and broke the removable connectors that plugged into these socket receptacles, I removed the receptacles by force and soldered thin wires directly to the pads on the PCB.
The following picture shows the keyboard after drilling holes and installing key switches. It shows black key caps on the key stems, but this is before the trackpad was screwed/velcroed in its final resting place.
When I re-started the trackpad experiment the last days of November, the trackpad had been electrical-taped in place over its frame that covers the opening. I had drilled/nibbled a hole for the trackpad mid October, and failed to please myself. My tolerances weren't good enough to mount the trackpad from within the keyboard enclosure. Thus the external mount with blue electrical tape. It concealed my cutting errors, and held the trackpad without allowing movement.
Yet the electrical tape itself was too thick. The areas under the tape were not able to control the cursor. To access the full trackpad surface, i needed somehow to back-mount the trackpad element without covering the front at all. Then I lost motivation for two weeks, thinking of what to use. I ended up using velcro, because it was the closest thing to double-sided tape in the house. This raised the trackpad surface higher than the mouse buttons, a sensation I'm not sure will remain acceptable long-term.
So this started as a trackpad mod. Why add three keys?
Because they were there in my tool box. They were added so the left hand could press Space Bar and Enter, two keys that are regretfully absent from the left side, and missed when one-handed typing is going on. They are simply wired in parallel with the regular Space Bar and Enter keys on the right side. The third key was drilled for completeness, and was for future use. Unfortunately I learned from use that keycaps on these new keystems protruded too much for comfortable typing with the left thumb. I kept pressing (my) Enter and (Kinesis') Delete at the same time, intending for only the Delete key. I'll have to countersink the three keys to achieve comfort and allow accuracy.
Erk, midnight. I'm a pumpkin. More details later ...