Thanks! I haven't ever played with Mathematica, no. The SVGs I've created were all cooked up in Adobe Illustrator, although any decent vector editor would do. For the diagrams with any nontrivial geometry, such as yours here, I usually write a C program to output Postscript, which is then imported into Illustrator for finishing touches. This workflow is probably heresy to people who actually understand Postscript, and it's not terribly efficient, but it works!