I managed to epoxy all three fins without getting any of them backwards. Barely.
Next step was to pull the fin can out of the body tube. I cut out the cardboard at the ends of the slots. There were one or two places where, despite efforts to avoid it, a little epoxy had gotten onto the slot, gluing the fin to the tube. It required just a little knife work to fix that, and then the fin can came out. I drilled a ¼” hole, installed the eye bolt (with epoxy on the threads), and epoxied the forward centering ring to the motor tube and fin tabs.