The 6 cyl springs are weaker than the 8 cyl. So the compress more, and have more stored energy. When when wieght is lifted, or pedal is touching the floor, it has more energy to release, or faster and higher to uncoil. the perches are great because the stock ones, ESPECIALLY new ones don't move much. So when the front tries to come up, and the a-arm should drop, it really can't. The perch is so stiff, it actually tries to rotate the top of the shock 12 oclock to say 3 oclock. This binds the shock and causes the front to slowly raise, and limits the front rise to the amount the perch is actually willing to move...which ain't much.
I love the 6cyl and 90/10 around town. Yes the front end comes up a little, more and more the harder you hit it. But still not bothersome. The perches made a world of difference in the way the suspension acts at the track and in town. Much more smotth. Thanks for the idea Jon.