Rear suspension design help

Guys, I have a few questions in regards to rear suspension design. *First off a little background. I have lots of experience in regards to double wishbone suspensions...only on the front of an oval track late model and oval racing snowmobiles. *I know the ins and outs with regards to bump steer, roll centers, castor/ camber gain etc. problem is they have solid rear axles. I have a Pro Mazda tub with front suspension and I'm building my own rear frame with a 1000cc bike engine. I have a clean slate as far as rear suspension design, but I would like some insight. *I have searched this forum, and learned quite a bit, but I still have a few questions.



Question #1. *



I've read some things about rear bump steer. I'm a little confused by this. Assuming that the toe arm is one piece with the wishbone (shaped like an N), and it is in the same plane as the wishbone, how can there be any bump steer? *I just don't understand how that is possible. *Along the same lines, does it matter if the toe arm is on the upper or lower wishbone? I've seen pictures of both and know that the lower wishbone can pass through the diffuser, and it would be better suited on top for this reason, but is that the only difference?



Question #2.



I see that on a lot of designs, the wishbones do not run parallel to the chassis centerline if looking from above .Specifically the front inboard mounting points are further apart from each other than the rear inboard mounts (in terms of side to side). *Is there a reason for this? Is it just a packaging deal? *Are the upper and lower inner pivot axis parallel to each other?*



Question #3.



Generally speaking how do the rear rocker ratios compare to the front? And same thing with regards to spring rates?



Thanks for any helps guys, Jeff