Good research there Jazzy,
The medium scale is a surprise to me because I believe there was only one "mold" used for the graphite neck experiment back around 1980. But the photos reveal quiet a bit of space beyond the tailpiece and the fingerboard ending just as the body begins, so it does appear to be medium scale simply by offsetting the bridge, tailpiece and using the shorter fingerboard.
Structure-wise, they are made up of a kind of 1/2 round trough which is then capped with a graphite plate making a structurally solid "beam". Much of the neck could be hollow but I also know they used quite a bit of graphite so the thinnest parts of the neck could be solid from front to back.
There is no truss rod so any serious change to the action would need to be done through fingerboard and fret shaping. That said, it should be as flat as it was when it left the factory in 1980. Bridge height should do whatever you want to the action unless you really prefer a big "bow" in the fingerboard.
I will add that the sustain, compression, and evenness of the sound resulting from this super-solid structure is pretty amazing. My original 1980 Series I fretless is graphite and I feel lucky to have happened to have it built right at that moment. For the fretless, that added sustain and compression is a lovely thing!
Side story: I loved that fretless as soon as I got it (and still do!) so I had a fretted version built shortly after. I played that '82 fretted graphite bass on a couple tours but decided the compression was too much for me in a live situation. I felt like I couldn't play as dynamically as I was used to with my wood bass. So I had that bass rebuilt as a fretless which serves as a backup to my original. But here's the thing .... I happened to play it in its original form on a Holdsworth tour which resulted in a video from 1984 - and I like the sound. The natural compression actually recorded very well. The joke's on me!
Jazzy, you should go check it out and see what you think, you may really like it! Let us know.
Jimmy J
