Hey Baz, I know I'm no longer a frequent contributor, but I'd like to slip in a recommendation.
The new JJ Excelsior is excellent, but I believe there is one thing lacking. On the prime universe one, the pylons connect to a module that is connected to the rest of the secondary hull. I think this module should be retained. In my own sketches of a potential JJ Excelsior (which I don't have anymore), I kept this module, and due to the size up-scaling of the JJVerse, I had it house the warp/transwarp core.
The logic behind this was that in case of catastrophic failure of the experimental warp/transwarp drive, the entire warp drive assembly - pylons, core, main engineering - could be ejected.
Just thought I would throw this out there.