^Heck, personally I like to think that Enterprise herself was refitted with a secondary hull sometime during the Romulan War. The books never say it wasn't, despite what the cover of To Brave the Storm shows.
Hmm... it would probably take a fair bit of time in-universe to do that. I don't recall the RW books that well; was there enough "downtime" for Enterprise
during the war to fit a refit in?