Interesting. I've been working on getting a fretless EB-3 for probably 15 years now, but gave up Gibson.
I have to admit, none of the wood/body types of Gibson shortscale EB basses really works without frets.
I tried every possible combination of electronics, including positioning of pickups, LoZ pickups and strings but no luck.
Not even the bar bridge helps (Uwe can use this comment later if he wants to). The best so far must have been the SB300 I got from Scott, it needed a fret job so I tried it out as fretless for some time. But it was never better than OK, so I put frets back on.
In the end I built a body (60's EB3 thickness) out of an Abachi/Maple sandwich and a really fat laminated maple/katalox neck with a thick slab katalox board. I could hear it was better even as I strung it up the first time, it really sings. Can't wait to have it finished, hope to post a project here when it's done. I guess it's the woods that make it good, but I do have strong belief in a fat neck being better for this instrument.
Of course, now I want to build one with frets too