Narita’s remark tells us that the soft-looking appearance of the costume was somewhat unsatisfactory to him as it is meant to be an alien with the solidity and rigidity of the armor, so he seems to have thought of bringing the costume sculpted by Takayama over to Gunji modeling factory where such props as the Ultra Hawks were made.
It is interesting that the costume photographed at Takayama’s Atelier May apparently has a shorter and smaller head while what happened to it is left unknown even though at least the height should obviously have been extended sometime later.
As to the suit actor who played this alien, it had long been told it was Eiichi Kikuchi who acted Ultraman in “Return of Ultraman” in later years, but Kikuchi himself says in a book he doesn’t remember it at all.
Tetsuo Yamamura says it could have been Kunio Suzuki as he remembers he felt it was a bit shame to find the good-looking costume didn’t fit Suzuki perfectly. There is an explanation that the human-sized Alien Borg was played by Kikuchi.
In my personal experience, I vividly remember one of my friends knowlegeably told me that this was the kaiju who would appear in the Ultraseven episode to come next pointing at the cover of an issue of Shonen Magazine (above) we happened to find when we were kids and the series was just being aired for the first time.
I found a blog seemingly run by the daughter of Soya Kondo who played the human form of Alien Borg by chance, and the daughter writes it makes her happy to find her beloved mother still stays in people’s minds through the show Ultraseven.