Less talk. More pictures. Something like this:
I see what you're thinking... but I'm afraid you're a little bit "tied to preconception" there.
If I were doing it, I would not try to create "TOS/TMP" style pylons at all.
I REALLY like the "keel" and I would not eliminate it. However, you can have the "keel" go to a "rail" that runs straight aft, to the ring(s). I mention this only if the rings are too far aft to intersect properly with the "neck" portion of your ship. I mean, the "keel" need not all be linear. The keel is only the main structure element. In my 1701, my "keel" consists of elments in the dorsal, in the secondary hull, and also the nacelle pylons, after all.
Again, I'd probably have two rings, rather than a single one... much as MJ did on his. But I'm not sure if that's my OWN "preconception" or if it's for some subconsciously-driven "function" idea bouncing around in my skull.
I get the point you were raising about seeming "imbalanced," and I don't object to a pair of upwards "pylons" as well... my issue with what you've done there is that it seems like you're trying too hard to replicate the 1701 we know. There are a lot of other approaches you could take to get some sort of "upright" that would serve that same purpose, but would not seem (and I'm not trying to be obnoxious here) as "derivative" as that strikes me as being.
One possible approach... have a "rib" going back along the back of your secondary hull, maybe 1/3 of the way from the "neck to secondary hull attachment"... and then have either one vertical or two angled ones go from there.
If you go with two, I'd have them at exactly 120 degrees from vertical. Symmetry is generally best from a mechanical standpoint and I think it would work better from an aesthetic standpoint as well, in this case. So all three "pylons" (including the neck extension going down) would be 120 degrees apart from each other, radiating from the center of the ring circle. You might put the impulse engine at the back of this rib, rather than on the disk proper... or you might split the impulse engine structure to "straddle" these features.
The one vertical, or two angled, upright supports would leave the secondary hull "back rib" and would have to angle to hit the ring structure. In this way, it would be reminiscent of the TMP structure, but for a real, sound, practical reason.
I've been thinking about doing a quick-and-dirty version on my own, just to show you what I mean, but I don't want to steal your thunder here. Just giving what "helpful advice" I can... which you may feel free to reject!