I built some sphere and circle sections. Copy and add them to your custom shapes. Copy/mirror them together, and you got a circle or sphere. By stretching during placement, you can get some neat ovoid and elliptical shapes.
They're not perfect, obviously, but I'm pretty happy with them. These shapes are pretty big, each like the size of a focused warship. so if you reduce them, the warts will kinda melt away.
I started on a torus, for the classic scifi engine intake hood shape. Then I realized it wasn't going to work as I wanted. After that, even, I think i kinda painted myself into a corner with the build and couldn't figure it out so I stopped. If someone wants to, you're more than welcome to finish it.
Believe it or not, the circle was more difficult than the sphere. Once I got started on the sphere, using the circle wedge as a template, it pretty much forced it's will on the build.
File is attached at the bottom as a zip.
If you use it in a build, please mention "Monsto's Roundish Stuff" in your description.
Here's a few pics. Full Gallery http://imgur.com/a/uhwnN
roundness.zip