If anyone can get their hands/paws/talons (or whatever pseudopodia you prefer) on a copy of the (now out-of-print) Dark Empire Sourcebook from WEG, there's a size comparison chart somewhere in it with the silhouettes of the ISD, the SSD, the Dungeon Ship, the World Devastator, the Sovereign, and the Eclipse (I). I've been assuming that the Eclipse II is about the same size as the Eclipse, just with a different spaceframe.
As far as size, the Eclipse should live up to its name; dwarfing even the SSD. But then, all the cap ships in XWA are too small.
http://www.xwingalliance.com/forums/frown.gif)
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"Abandon head!!!"
[This message has been edited by Flying Beastie (edited April 28, 2000).]