I have checked the archives extensively and still not clear on the ideal size (if there is one) or if there are other issues that have cropped up (ie: rubbing, performance, alignment / tire wear, vibration).

It seems that aesthetics are the main factor although the forum seems divided on this issue ie: 10mm front and 12mm in rear while others like the wider 20mm.

I have checked prices as well and find H&R to be quite high. The Eibach pro-spacers seem much more reasonable and of the same material and quality. I can get (4) 10mm spacers with longer bolts shipped for $129.
As far as rubbing or tire wear - it is not clear if these are really concerns or not.