I certainly agree that 2.5" of arrow might as well be 2.5 feet when it comes to changing the spine of an arrow.

The chart is relatively vague (as you no doubt know), if you list your arrow at 30" (which is typically what I suggest for 29.5"... always round up) and go with the #age bracket 62-66 with a 100gr.... the chart/selector will tell you to shoot a 3-60.

You know better than I surely about how binary cams (I'm shooting an HCA Iron Mace... Trinary cams... close to the same difference) react tolerance wise to stiff/weaker spines. I've read posts and opinions and so forth, but you have access to data and tests that the rest of us don't. Its my understanding that the binary system is much more tolerant/flexable/forgiving of a weak spine than say a single/one cam system. I'm not sure why, but is that correct?