Rear suspension design

Im asking here because you FB guys seem to have a lot of experience building cars similar to whatbim trying to build.



I've started drawing out the rear subframe for my car (bike engined with carbon tub). This is my first IRS car so I'm a little in the dark. I have a wheelbase of 102-103" I've taken some quick measurements off of a Formula Renault to get me in the ballpark, but I can't completely copy it because of differences in engines. I'm looking for answers to a few questions and possibly someone to run a few numbers thru a suspension program (or a link to a good free one). This is going to be a track day car, and if your worried about sharing information, you could PM me and I promise it will stay between us.



I have a pretty clean slate. With the engine I'm using, the side plates should be ~8" outside to outside. I also do have some axles and tripods that I'm planning to use. I'm building my own uprights, wishbones, etc



Questions:

#1. - how much camber gain should be designed into the rear suspension?

#2. - Where should the rear roll center be?

#3. - I'm going to make my own body work (diffuser too). I'm going to make the toe-bar part of the upper wishbone, but is there any other "aero" concerns I should know about??



Thanks again for any help!!!