In Lith, box mapping sucks, avoid it if you value your sanity.
It looks like a stealth fighter model, so I'd suggest using decal mapping to break it in half. Like use the decal map to UV from the front, which will give you a view of the front of the ship. With this, break off the top polygons, like select the top polygons and then deselect the verts that are shared with other polygons. you want to peel the top off the ship so you can then decal map from above, and get a nice map to texture onto. By breaking up your model and using decal mapping, you should be able to arrange things quite easily to capitalise on your texture space.
The other handy UV mode is cylinder mapping, that would take a cylindrical mesh and kinda unroll it like wallpaper. It should be obviouse where you'd use this method, I like to use the capped option all the time, so it get's a lid if it needs one.
It takes a lot of practice, and Lith is not the most intuitive package, but it's free and it gets the job done, so I guess we have little to complain about.
Van-B
Put away, those fiery biscuits!