I have recently discovered and understood the math behind viewspeed v2, which is the sine ratio, and I find it very comfortable. IMO sine ratio really captures the perceived sensitivity on screen.
In addition, from what I have read, for viewspeed v2, the radius of the arc crosses the VFOV points, i.e. the top and the bottom of the monitor. It might work for some people who sit at a certain distance at the monitor, but I believe the calculator would be more complete if a percentage monitor distance variable is added for where the arc crosses, just like monitor distance for the tangent ratio. It could be based on HFOV, so 100% represents the arc crossing the monitor on the left and right edge, which is consistent with the percentage of the monitor distance in the tangent ratio. The result is that people can customize it based on how far they sit from the monitor.
Another interesting fact of the sensitivity curve for sine is that it tracks really similarly to that of the tangent ratio, just with a different monitor match distance. I have plotted graphs on Desmos to verify that. For example, the curve of 56.25% distance sine ratio, which is 100% of VFOV, almost overlaps with that of 70.3125% distance tangent ratio, which is 125% of VFOV. I can use 70.3125% monitor match to obtain sensitivities for 100% VFOV sine ratio matching with very little deviation.
Personally I am using 129% VFOV matching, which corresponds to 103% VFOV sine ratio matching.