Don't know what the difference in scale length is,
But figure this ---
The TOS Enterprise is 947 feet long (according to most authorized sources).
They say 289 meters long for TOS; 305 meters for the Refit ship.
The Refit Enterprise is roughly 1000 feet long -- most of that difference is noticeable in the wider diameter of the Refit saucer. The Refit nacelles and engineering section are very close in length to the TOS Enterprise. There are sources that get it wrong and say the Refit nacelles are longer than the TOS Enterprise. There's hardly a difference from what I've seen on many sites. Even cross-sectionally, viewed from the front and rear, the two versions' nacelles are very close in diameter.
(Cross-sectionally front and rear, the Refit nacelles appear to be round. The flat grilles on the sides are what make those nacelles look more rectangular than the TOS version.)
Don't know how that difference in length works out in inches when you scale them down...