I finally figured it out. NO, I didn't work on it for last 6 weeks. I just came back to it today and looked again at the various parts with new, fresh eyes. I was a bit too literal when I copied the key for hover in org.cinnamon.gschema.xml and preserved the default value of false.
Scale and Expo have check boxes to implement hover in the cinnamon settings (I can never remember exactly where) but anything else would have to be done in the schema and recompiled. Give cinnamon a restart and you are good to go. Now this gives me pseudo-hotcorners an my top panel with launchpad at one end and Scale at the other. Using cinnamon settings I put Expo in the bottom left and, voile, I have 3 hotcorners.
I wrote this for launchpad (also known as slingshot sometimes). I would post this but a person would need to also compile launchpad. I use an older version that is more mac-like than the new version that is, well, completely different. I would accomodate any interest in this but, since I have never done this before, would need some instruction in how to post. I am having a problem with the icon (does not display) but I trust that it is just a minor setback.