RE: JeffB, this spine's for you!
Nubbb,
I just got this tester assembled this past weekend, so my tinkerings with shafts are very preliminary. In fact I still need to finalize the indicator mount I'm milling that will place the indicator DIRECTLY above the centerline of the shaft, and perfectly verticle (at least within a thousandth of an inch or so...). Currently I just have an indicator holder rod assembly, and you can position that in just about any orientation.
But as we get toward the outdoor field season and hunting season, I'll be trying a new batch of Navigators for field and ACC's for hunting. I do some work for other people and will be checking their arrows as they come through so I can get some idea of what's marketing advertising and what is for real....