I thought about filling the riser recesses, but I don’t have a router and decided, perhaps impulsively, to chisel/saw/sand to remove the flat and flip it over. I acted hastily throughout. I don’t need to hurry. That’s the lesson I need to learn. I could have avoided this mess if I had only waited long enough for mpilone’s post. Instead, I tried a stitch, and it seemed O.K., so I plowed ahead.
The deed wasn’t pleasant or pretty, but it’s done now. The flat wasn’t difficult to clean up. Removing the thickened epoxy from the shell was, and I didn’t remove 100% of it, but if the new fillet adheres well enough the remains of the old one, I’m O.K.