[@OfWindAndRain]
[quote=@Alfhedil]
Well, thing is that a suitably advanced species could find a way to power exodus ships like these Arks without having to dump so much material into them, not to mention most of the space the ship occupies would be dedicated to the dwarf star anyways. During the long voyage, the ships could rely namely on scoops for the intermittent material scattered in the void, and stored reserves. Since most of the inhabitants will be on stasis anyways, and you mentioned that the ships are relying mainly on their initial velocity, the only power the ships would need to expend would be on maintenance.

All that considered, they wouldn't need to be quite as large as you have them now, but could still be relatively sizeable. This is even taking into account that there would only ever be one or two in this galaxy. Bigger is not always better after all.
[/quote]

on top of maintenance you also need to run the stasis field generators for millions of years, so you really need some kind of long lived power-source. Also the arks are suppose to be massive unwieldy monuments of hubris, because the only reason they built them rather than, say, firing hard drives filed with brain blueprints at other galaxy using rail cannons, is their elitist focus on having your original body. That said, I agree that a spacecraft twice the size of Jupiter is excessive so how about:

An ark's primary component is the dwarf star that has sustained it's journey across the void between galaxies. these stars are so small they are on the verge of being classified as gas giants but they are incredibly long lived and stable  , making them n ideal source of power for systems requiring eons of operation time. this star is surrounded in a web of energy collectors that harvest heat and light from the dull star to power the stasis units holding it's dwarven passengers, and an array of magnets and shield projectors that hold the star steady in the grasp of the ark. the rear of this rig features a large array of boosters that initial sped up the ark and will also be used to slow it down upon arrival. At the front is the only solid part of the web, a ship/station, known as the Hearth, that is about the size of Germany. the Hearth houses everything the Mayall need to start restart their society in a new galaxy, such as the stasis held Dwarves themselves, backups of Demi minds, cloning equipment, bio material for slave/food production, manufacturing facilities and a vast array of smaller vessels docked in hangers or on it's surface. 

also it probably shouldn't be in the military section