Douglas Trumbull and his team built the large refit Enterprise for TMP.
This is a relatively minor point, but Douglas Trumbull's and Richard Yuricich's company Future General Corporation finally took over the effects for TMP in March 1979 after
the final filming miniature had been designed (by Andrew Probert and Richard Taylor) and built (by Magicam) while it was being painted by Paul Olsen. So Trumbull and his company were only able to add finishing touches to the model.
Believe it or not, Trumbull states in his interview in Cinefex #1 that he believed the Enterprise miniature was one-fourth as big as it should have been: "In 2001
, the Discovery
spacecraft was fifty-four feet long. But in Star Trek
, the Enterprise
is barely seven feet long; and it was just an enormous struggle to get not only a sufficient degree of detail, but also camera angles and depth of field and lighting that worked."