Thanks for everyone's help on this issue.
What this was all about, is that I wanted to show the effect of using a 360 Panaromic HDRi image as background for rendering, and a smooth dome makes it easier to see how the HDRI is reflected. I wanted a good tool to make a quick, smooth dome - especially for reflection examples.
The image below uses a Free HDRi provided by Bryan James. He made a 360 photo of the interior of St. John's Cathedral in NYC. The Sketch Up model is a reflective ground plane, and a reflective dome.
Everything else is generated using the HDRi for lighting, shadows, background and reflection.
[image: Z7Y9_stjohnsHDRI.jpg]