CenterDeck,
If you can get your hands on one of the sketchbooks made from the Star Wars movies it shows a great comparison. If you look at the first three movies, Episode 4 - 6, it shows the Rebel Blockade Runner to be a quarter or less the length of a Star Destroyer when it is taken inside a Star Destroyer at the beginning of the movie. In Episode 6, they show x-wing flying by another Blockade Runner class starsghip and it looks a little less than half the length of a Blockade Runner. Now taking the comparisons, an x-wing to a Star Destroyer is like a tricylce being on an aircraft carrier (Nimitz Class). This is a rough comparison but it works for visuals.
Oh, great looking Avatar....The Seabee patch!