Okay, but I don't see how making the surface area for the pylon-secondary hull so small could help with warp/slipstream field efficiency (is that is what you mean by Field geometry/efficiency). I'm no suggesting making the nacelle pylon thicker by it's sides (the fore/aft). I'm suggesting making it thicker by increasing the surface area of the pylons from the top/bottom, and not by a whole lot. Maybe the same amount of surface area similar to the pylon-nacelle attachment points of the Prometheus class, only applied to the attachment point for the pylon/secondary hull, and combining that with the curves you already have. You know what I'm thinking?
This is your design, so if you ultimately want to leave the nacelle pylons the way they are, then I'll respect that. I just wanted to make sure that you can visualize what I'm suggesting first.
Bigger =/= Better
That said, the fact that hull shape effects field efficiency is established. How that works is not. It's just a convenient way to justify how the ships are shaped.
Were I writing the technobabble on this ship I would probably posit that pylon attachment is designed to minimize that section of the hull's interaction with the warpfield, in order to tune the "sustainer effect" coming off the warp ring's field coils.
But that's just technobabble to support what I did there (both in terms of cross section and the way the pylon bends.
I'm not exactly averse to toying with the thickness of the attachment point, but I will tend to hesitate, with a certain amount of reason. Right now the top of and bottom of the attachment points sit directly on a deck line. Lifting the top will pull it, and the shuttlebay floor, off that deck line.
Lowering the bottom would require a major rework of, not only the hull, but the interface with the warp ring.
That's a lot of effort to satisfy what is, really, a minor quibble.
Beyond that, I've looked into the Prometheus's pylon attachment, and I can't see what it is you are getting at. if anything the z axis on those pylons is much thinner than what I've done.
Could you, perhaps, elucidate?