I have been playiong around with spacers overe the last week or so, and admit that the initial advice was 10mm front and 12mm rear.
im on H&R springs and have just taken my summer wheels off for a refurb, and reverted back to the standard 18's.
wanting to push the envelope, i decided to go for 12mm front and 15mm rear and see what happened.
15mm on the rear was a step too far and it gave me a rub issue that was beyond somethiong you could live with. so the 12mm went on the rear and under a heavy load you get the odd rub, but no great issue.
this left me with a dilemma, and i opted to put the 15mm of the front and below you can see a pic. it works fine, the fronts dont protrude and are right on the limit. Given my time again, i would go 12mm all round, but the 15mm front does work.
i drive my car a fair bit and do a fair amount of track work in a radical so have some idea of knowing what works and what doesnt from a performance perspective.
the front end bite is now about as good as its going to get and i was surprised at the difference it made, and the overall balance of the car with the ARBs, springs and spacers is about as good as its going to get for what i need.
i appreciate this is different to the tried and tested 10mm front 12mm rear option, but is just my 2c's and my experience.
below are 3 pics. one standard the day i got it, the second on the 19's, and the third back on the winter wheels.
i hope this helps.
s