Ies

Studies have shown that IES does not work when the correct rate is below 90%; however, “seeing this stimulus to press this button” is not complicated work, so the correct rate is over 90% in most cases.

These names […] may form regular plurals; thus, Aes, Bees, Cees, Dees, Ees, Effs, Gees, Aitches, Ies, Jays, Kays, Ells, Ems, Ens, Oes, Pees, Kues, Ars, Esses, Tees, Ues, Vees, Double-ues, Exes, Wies, Zees.

1998, Ricardo Corona, "These Esses" ("Esses esses"), in Other Shores (Outras Praias), translated by Ricardo Corona & Charles Perrone to say (full of ees, ies, ues) that plurals are always two or more