I like how you're focusing on the 'business-end' of things with this starship =).
Re-undercut: Maybe you could under-exaggerate it, and get back some usable space?
I sketched this up one night, tracing some of Shaw's work, and basing it off of what he called the 'conjectural hanging edge structure' - perhaps the undercut we saw on the show/the model was supposed to be a hanging edge, not a huge cutting into?
(This sketch would be for a ship greater than 947ft...)
(The red were parts I was proposing water/liquid/gas tankerage and life support sub-systems)
"If you need a holodeck to make an interstellar starship on the bleeding edge of the unknown
interesting, something is seriously amiss."
- Straczynski & Zabel