In my opinion (regardless of what source says x size), the JJ Connie would be pretty close to the same length as the TMP Connie. The most damning evidence for this, is that the saucer is virtually copied from the TMP version.
I'd hardly say that's conclusive. What is much more conclusive however, is the scale of the view screen window, the shuttle bay, the shuttles flying over the saucer and the large cavernous interiors. I really don't want to fill Baz's thread with this again but if anyone want's to have a civilised conversation about it then I'm open to pm's.
Baz: I don't know how feasible this is for you(I know very little about the process of BC ship modding other than, you know, making the model); but perhaps including two versions in the download, one roughly scaled to each size would be an idea? Would allow people to choose the scale they want and avoid becoming embroiled in this debate again. Personally, I've been dying for a canon sized 'New Enterprise' to use in screenshots for a long time!
