Actually, though the gimmick to make the mouth of Ultraman movable was abandoned, the
same attempt was made about the head of Ultra Seven.
The slit of the earliest head of Ultra Seven is likely to show the trace of an attempt to make the lower lip and jaw movable.
And then an attempt to move only the lower lip movable was made.
Finally, like Ultraman, the idea to make the mouth movable was given up.
With regard to the eyes of Ultra Seven, the eye holes were put in the center of the eyes.
Looks like Tohl Narita found it so regrettable that he had to give Ultraman the the eye holes inevitably at last.
He was thinking of finishing the eyes of Ultraman by fitting transparent plastic parts in the eyes to secure the visibility for Satoshi (Bin) Furuya inside.
But due to the shortage of time, he had to just drill holes under the eyes.
Mr. Furuya says in his memoir (“A Man Who Became Ultraman”) that Mr. Narita looked angry at that time.
After a while, it’s likely Mr. Narita told Mr. Furuya how much unwillingness he felt when he had to give the drill holes to the eyes of Ultraman.
Regarding the A Type head, you can see the eye holes become bigger to increase the visibility as the shooting progressed.