Should the RC:FC ratio be calculated at sag? - I've been thinking about this too. I'm not so sure it should be. When we ride, of course we moving the suspension a lot, and we will travel at sag and way beyond that on a ton of the ride.
But, we are still in many situations that we are unweighted / less than 30% sag when riding. Popping over roots, jumps, whatever.
When this happens and we are unsagged, our rear lever point (the rear wheel) is still part of the FC:RC ratio, and can touch down further forward than a longer CS, which in turn effects the balance of the bike and the way it behaves.
I see the sagged chainstay measurement as just another data point to guide us on bike geometry. My crestline (not a High Pivot) also has a rearward axle path, not as aggressive as the Velduro, but still has a decent amount of growth at sag point.
If we start measing FC:RC at sag point, then we must also consider the fork is also sagged, further changing the FC:RC ratio.
Finally, bike geo charts are also just a guide.
Almost every single one Many are incorrect when the real bike is measured! They are based on CAD, which ideally would be perfect. The closest I've ever found is Nicolai. Their bikes are exactly as the data shows on their chart (well, I measured 2 so far and they are spot on).
Crestline axle path
View attachment 172853