With work on some careful design, the 3 link works quite well road racing.... It does take a lot of testing and adjustment to get it right. Back in the late 70's some of the IMSA teams (GT and GT/O) used it, primarily the BMW team that Haywood drove for... Bolus and Snopes also had one on a Mustang (now it would be a GT-3) car, got to get a bit of first hand experience with that one. With reasonable good mechanical drafting skills you can draw it out and plot the movement, which will answer your question on the length of the upper link. The shorter upper sacrifices pinion angle, done correctly less then 1 degree of change, which can actually help acceleration out of a corner, in favor of anti-dive for braking and anti-squat on acceleration.