Actually Mooster you dont need to modify the meshes in a mesh editor, Newbeorg has a resize tool i found here in the forums that can resize if for you, you simply point to the mesh file in particular and select an output folder, click the size you want and press go!!  It is what i have used for planets and ships in my rather little mods.

Remember though, that if they get toooooooo BIG, that the textures dont map properly of course and they look.... how to say?  Yucky!!!    But find the tool and give it a try, its easy and you'd probably be a wiz in no time.

-Teal