The physicists and engineers may chime in, but I do wonder if the fact that the two springs, being situated between the front tire, rather than it being a single rod in line with the tire, can have a meaningful effect. For example, the regular (and most of the aftermarket) Birdy spring will likely work great for hits that take place near the center of the wheel's trajectory. What happens however with off-center hits? Or are suspensions like the MultiS as stiff as, say, Cannondale's Lefty? Because that would be pure b...ls..t

Is having a spring a bit closer to an area of impact completely unimportant? Or two springs to carry and balance out the load of offset impacts? Perhaps it's negligible! Ideally some tests are performed at some point of the various options out there.