I appreciate both of your replies.
- Duplicate array is useless for me because you have to input the duplicate angle.
- Using a circle as an overlay to truss seems like a workaround to a feature that should be working. But oh well that's what works for now. If I place the fixture on the circle, why does dup on path shift the fixture I placed 90 degrees from it's original placement? Then I have use the rotate tool to put it back, seems like another workaround to something that should work more straightforward.