All this suspension geometry stuff is a bit of a black art to me. I started trying to understand more of it just recently. Until then i followed some words of wisdom from a suspension guru, who told me "You could do alot worse than copy the fastest car in the class". Getting a look under the fastest car isn't always that easy, because chances are he knows what you're up to cause he used to do it himself
scrub radius. its the distance from the centre of the tyre contact patch to where SAI intersects the ground.
'+' scrub radius where the centre of tyre contact patch is outside SAI, '-' where its inside the SAI.
SAI = Steering Axis Inclination. On a strut front end, its simply an imaginary line drawn throught the centre of the strut. Or, it you have bent struts, it's a line drawn through the lower pivot (balljoint) and the top 'pivot' (where the shock insert bolts to the strut top)
Strut front ends apparently don't like lots of + scrub.
Obviously with a given wheel offset, the only way to alter scrub is to alter the SAI. Movint the top of the strut inwards will do that, but also move the centre of tyre contact patch outwards to a lesser extent, so you can't really alter it all that much.
anyway, all i really know is my +3 offset (103mm backspace) 7" Hotwires work much better than the -10 (90mm backspace) offset 7" superlites I had. Would other less offset wheels work better? I dunno...