To make both Enterprise and Reliant, you need to make a spoke ring, and at the end of the spokes, add the trapezoidal hull peices. Rotate them to make them almost flat. You have to make a second ring for the bottom. I inverted the Radio dish piece to make the center, and to finish off the saucer, you have to use the giant wheel like peice. You have to get it just right, in the middle. You add the Window sections to the perimeter of the saucer.
The Enterprise requires the engineering section, and I put that together with multiple rings and cowling type of peices. When you need to have something inverted, often you have to attach an antenna, then attach the peice you want inverted to the end of the antenna. (like the connection peices betwwen the saucer and engineering sections).
I took advantage of a bug to make Reliant. If you invert a white "lighted windows" rectangular piece, you end up with a free floating hardpoint, a short distance away for the piece.. That's what I used to start the midline part of the superstructure to which the engines were attached.
BTw I made these and Klingon ships above without mods. I'd love to load them into the library, but I can't figure out how. What files do I need to transfer to the library?