I realized I could use a 1-2-3 block as an instant touchplate - no need to even solder anything. I put a video up at Using a 1-2-3 block as an XCarve touchplate - YouTube.
I got the blocks off ebay - 3 MATCHED PAIRS 6 PCS PRECISION 123 1-2-3 BLOCKS BLOCK 23 HOLES .0002" NEW # | eBay
You can also use them for z axis calibration - Using a couple 1-2-3 blocks to calibrate the z axis of an XCarve - YouTube