Rogue NineCH, thank you for the PM, I was out of town over the weekend and had missed this thread. As to comments...
I would have to agree with the sentiment of having standard sized warp engines. The larger ones do look a bit ungainly, imo. The secondary hull for the BC should be larger in circumfrence, but your "skinny" design got me thinking. If you used the skinny hull, throw on LN-68 engines, and the design would make a great TMP era Fast Cruiser (CF), which I don't think anyone has ever made before. What do you think?
Oh, one thing...a BC probably wouldn't have those big arboretum windows, heheh.
Here's a couple of pics of a TOS Battlecruiser...
I'm still hoping to see all four BC varients...