When did they say the Constitution ships were delayed for a decade? Did I miss that in the film?
I did a little figuring; see what ya think:
For a 3000' ship:
The saucer width would be 1311'.
The viewscreen would be ~35 feet wide.
The oblong windows in the saucer would be 15.9' x 5.8'.
The portholes in the saucer would be 5.8' in diameter.
The secondary hull docking port would be 15.1' in diameter.
For a 2378' (725 meter) ship:
The saucer width would be 1039'.
The viewscreen would be ~29 feet wide.
The oblong windows in the saucer would be 13.2' x 4.8'.
The portholes in the saucer would be 4.8' in diameter.
The secondary hull docking port would be 12' in diameter.
For a 1597' (487 meters) ship:
The saucer width would be 697'.
The viewscreen would be ~18.5 feet wide.
The oblong windows in the saucer would be 8.5' x 3'.
The portholes in the saucer would be 3' in diameter.
The secondary hull docking port would be 8' in diameter.
For a 987' (301m) ship:
The saucer width would be 431'.
The viewscreen would be ~11.5 feet wide.
The oblong windows in the saucer would be 62" x 23".
The portholes in the saucer would be 23" in diameter.
The secondary hull docking port would be 5' in diameter.
Strangely enough, if one assumes the 301 meter length, the measurements are extremely close to TMP Enterprise.
TMP Enterprise: 304 meters long.
The saucer width would be 465'.
The oblong windows in the saucer would be 57" x 25.5".
The portholes in the saucer would be 25.5" in diameter.
The docking port would be 5.3' in diameter.
The problem with the ship being much more than ~300 meters is that the bridge winds up being
massively larger than it is. The viewscreen is about 136 inches (11.3 feet) which corresponds to a 301 meter ship since the viewscreen is really a window on the front of the saucer and it's size is easily compared to the width of the saucer. If the ship were 725 meters as ILM says, then the bridge would need to be sixty or seventy feet wide....it ain't.

Even if the shuttlebay is larger than a 300 meter ship can carry, the bridge is the primary set for a Star Trek ship...it
has to fit the model.