Thought I would add my late thought on this topic..
I have had three NT4 thumb basses over the years..I now have a January 1990 NT4. Very comfortable and slim neck, weight of a small country 4.8 Kg (lol) Wenge/Bubinga. Transitional stage..old school back plate and dots on the wenge fretboard, but not scalloped on back of the headstock for the Schaller tuners..EMG replacement pickups for the original EMG's like for like. MEC preamp. One for sale at Bassbros at the moment. I have owned this Thumb for 5 years now, and have had not had to adjust the neck once! The most stable trusrod neck I have ever owned. I find the wonderful contoured body on the bass now works quite well with my 57 year old contoured belly (lol) The 89 I owned I deeply regret selling! This 1990 equally comparable..
1997 version..just nowhere as good, neck profile broader, the Warwick fundamental thump no longer there..
If in the lucky position to own an NT4 Thumb, I personally recommend buying an older version..That said I don't know what the new ones are like, bar very expensive.
ps If played through an old school Trace Elliot the bass sings!!