I dunno. I think the fins are cool. And what's more there could be a technical reason to have them. Most sci-fi ships totally laugh in the face of the laws of thermodynamics. These fins could be something related to the ship's heat dissipation system. Contrary to popular belief, hard vacuum is a wonderful insulator. A ship like this, that is continually producing power would necessarily also be producing a bunch of heat, and external radiators are pretty much the only way to dump it out of the ship to avoid baking the crew to a nice golden crisp.
Dennis and I have talked about the "sails" functioning as heat dissipators in addition to being part of the FTL drive system. He wanted to see them in an open--or partially open--position more often than just when the ship jumps through hyperspace. I think the current plan is to have them closed when the ship is in combat or traveling at high sublight speed, partially open when the ship is coasting or in orbit, and fully open when the ship goes FTL. Heat dissipation might be a good rationale for that.
As for the fins, I like they way they make the gaps in the aft ring look a little more purposeful rather than like someone took a hacksaw to them, but I don't like the way they add to the general clutter and complexity and shapes jutting out all over the place.
I'm actually struggling with the ring itself and have been for a long time. It looks pretty cool from the front or the back but seems to clash with the flow of the ship's lines from most other angles. I'm giving serious thought to a couple of different alternatives, including one that would relocate the big cannons on either side of the bow. Stay tuned on that one.
But on the other hand... and I hate to say this... I don't like the new fins. To me they disrupt the natural "flow" of the engine cowling and make the sides of the craft to visually "busy". I also think the sharp angles don't fit well with the curves featured everywhere else. But if you are intent on keeping the fins maybe you could move the angle from 45 to 90 degrees so the two fins are parallel with each other. I would also suggest shortening them a bit. That may give you the look you are after while keeping things more uniform.
Funny you suggest that. The original plan for those fins was to have them all horizontal like the wings of a bi-plane. I only did the 45 degree angles on a whim and was sufficiently struck by them that I decided to leave them that way for the time being.
Horizontal fins are still an option, but a lot depends on whether or not I decide to keep the whole aft ring the way it is or do something a bit different.