No. I never tried it, myself, either - just posted it as an idea. When I went on to attach mine, I ended up just using pin backs with locking clasps, which worked very well and without much fuss.
As I am working on putting my armor and vest together, my thought is that using magnets would be an excellent method to temporarily align the plates on the vest in preparation for using other fasteners. Possibly use magnets temporarily glued to well marked locations on the plates, then align...