[Raptor]

Thanks for your reply.

In response to your initial questions:

Yes a stiffer front bar will limit how much body roll occurs and transfer more of the cornering load to the front tyres. Reducing the bodyroll should also reduce the wandering, especially if its occuring as I suspect from the rear live axle steering the car as the suspension cycles. But this will come at the cost of some loss in compliance on uneven surfaces.

Sorry, can't help with sizing.