Lookin good guys
I know its just a mockup for the mothership, but the sphere on the mothership and the fighter could be optimized alot. Possibly not for the mothership though as the extra tris will help define the scale. At the least I would cut one or two loops out of the fighters sphere and use them to round off the lower section of the front.
One other thing I saw, is remember to watch out for ngons
Eitherway its comign along nicely! Keep at it!