Looking at the Excelsior, the ship conceived originally for transwarp drive, the nacelles were very long compared to other designs, allegedly the longest nacelle to hull ratio; which is probably relevant to the actual transwarp field which is like "warping the warp field".
So I would say the nacelles on the Horizon, the first successfull transwarp ship, should be even longer, maybe as much as twice as what is shown here if we are to follow the idea of the original proportions of the first transwarp ship to reflect that specific tech.
In our LF RP, it would be consistent with the fact that the only other ship we have with transwarp is the Lotus; and it can go only once, at best twice before risking burning out her assembly. And the Intrepid class has the shortest nacelle to hull ratio. So there seems to be some engineering logic\relation here.
I'm not fond of the "fat butt" look but with the Aquarius class docked inside aft, it does make sense. On my original collage, I used the secondary hull underbelly of the Intrepid under the Galaxy hull to represent that dock, considering the overall size of the ship. So I guess we can go either way to accomodate an escort class vessel back there.
Notice however that the Aquarius is found at the tappered end of the Odyssey class which is smaller than the Lotus class. So that would mean we may not have to bother with it and shape it any way we like