Here's another shot from the side. Less clear but it does look like the flange closest to the ear is the same size as the majority. I wonder what's going on in the screencaps from post #7
Also, I've heard this story repeated a few times: When filming began on The Motion Picture, nobody remembered to make Uhura an earpiece... so they shot a few scenes without one. There are some shots where no earpiece is visible, so it seems plausible. The story continues that after searching through storage, the prop guys found a box of old TOS props, including one of her earpieces. I just looked through TMP screencaps to see if I could spot it, with no luck -- in all the shots I saw (and maybe I missed it), she seemed to be using the movie style shorter, resin earpiece:
Is this a true story?