Here is how to finish these off:
Scuff up the backs of the plant-ons with a random orbital sander
Mask off neighboring areas to avoid getting epoxy on the nice gloss finish (note that the recessed areas of the body were not glossed to promote better adhesion between of the plant-ons) and glue them in place with 5-minute epoxy.
While the nozzles were curing in place, I found the best way to let them rest is as follows, otherwise gravity pulled them slightly out of axis with the central axis of the main body.
Give a final polish with a soft cloth
The plant-ons recess really nicely into the body by 0.5mm. Again, much praise to @Eric_Ardros for that idea.