The Kelvin's size is pretty consistant and clear - as detailed here.I think the Kelvin scenes in STXI were powerful, and had a unique atmosphere. The gigantic ship, with a cavernous engineering section so big, guys were rapelling down from the upper levels. Dozens and dozens of shuttlecraft.
Just a thought - when we first see the Kelvin it is before Nero arrives from the future and changes the timeline. This is in effect the universe of TOS.
How then, does the size and ships compliment of the Kelvin fit with the (smaller ?) TOS enterprise ?
I'm honestly not sure what the issue here would be. The Kelvin's size is actually unclear, but even if it weren't, so what? You'd have a ship that's larger than the Constitution class yet more primitive. No big continuity issu here.In fact, there's already precedent for earlier ships being nearly as large as the Constitution class yet being more primitive -- the D'Kyr class from ENT was seen in "In A Mirror, Darkly" to be very nearly as large as a Constitution class, yet more technologically primitive, especially in weapsons and defensive systems.
But, even so, they simply built them bigger in those days. End of subject.
The last thing I want in a Kelvin novel is the kind of nonsense that "explained" why the NX-01 Enterprise looked more advanced than the TOS one, like we got in the post-Enterprise novels (which, incidently, was blatantly at odds with the slaughter in "In a Mirror, Darkly")