Stuart,

I've set up an anhedral stab and just used the method you described in your first post. If you attach the carbon rods so they don't cross, but actually just come right next to each other at full down elevator, you can still compare them using this method. I've found that the space between them doesn't make a huge difference. Because you're essentially extending that elevator so far out with the carbon rod, small misalignments can be spotted pretty easily.

-Brett