Once I've decided which design I'd like to propose, I try to create images that illustrate the scale and form in a vernacular accessible to the client. Oftentimes this necessitates stylization in order to minimize confusion as to what is "real" and what is just placed into the image to anchor the sculpture and demonstrate it's scale. This is one of the many reasons I use SketchUp, since it's native output has a nice, simplified feel. At this stage it's also necessary to write up a statement that conveys how I see the work fitting into the expressed criteria for the project, a task that sometimes proves much harder than actually fabricating the piece!
I usually try to work through the entire project in virtual space on the computer in an effort to minimize surprises, including the whole unfolding process and structural details. Depending on the scope of the work, engineering consultations are handled at this stage as well. Once I have the project pinned down (meaning a signed contract and a down payment), the structural specs are double-checked, and the actual work can begin.
On this project, the engineers called for 14 gauge steel on the two upper rings and 12 gauge for the bottom one and the base. We were able to grok a rough estimate of 1200 pounds for the whole thing, which was used to establish what sort of anchoring and basing system would be required.