The one thing to be aware of with large ships (and stations) is that after a given distance from the player (a few scanner-lengths or so, I forget offhand) that Oolite won't draw them. Hence if they are big enough to still be visible at that range, they tend to just "blink into existence" or conversely vanish without trace if you're leaving them behind.
Its more than 'just a few scanner lengths'. e.g. the constations are still visible from the planet. Not drawing at all will only happen when much further away than planet-sun. And it will be an issue when creating ships of planet size.
What also could be an issue is that Oolite expects that the main entity is the biggest one. When the main entity is to far away to be visible, oolite doesn't bother to check further for subentities. The only example of that were the old ring stations. The central core was small and when that came in drawing distance, the big rings just popped into view. Svengali fixed that in the new release of the ring stations.