Thanks for the Report Ray, good progress.Do let us know how you get on, and what works (and what doesn't!). Adding a phase reversing switch seems like a good idea to me, and easy to do.
Theorising a bit... Depending on the separation of your antennas, you might find they get equal amounts, in phase, of the local noise e.g. if equidistant from the source. Remote (wanted) signals would also be received equally, but there will be a phase difference according to the antennas' separation and the direction from which the signal arrives.
Further thoughts off the top of my head... Try the canceler using one antenna connected normally, and the canceling input connected to the line to the other antenna, but with the feedline shorted at the antenna, just like the noise test.
Ed