Just talked to TireRack - last week they actually tested on a BMW 3 series the ZII against ADO8-R, G-Force and the RE-11. The report is not out yet.
Suffice to say that they liked the ZII and G-Force more. And the ZII may indeed minimize some of the understeer due to their harder sidewall. As to the width of the tire, it is pretty much the same as the RA1s so there will be some rub with 235/40. The G-Force tends to have a wider fit.
So perhaps for those who are not pushing real hard to the edge of 10/10 the ZII in 215/40 and 265/35 is the overall option. Total shipped is $936.53. At one time I thought they were offering special "cosnideration" to NSX owners (on record with them) but apparently this was never the case - the info was used to support the forum/club with advertisement I guess.
Edit: I should have added that if you have dedicated wheels for track, the option of using 235/40 and 275/35 RA1s will give you better grip/experience and they are only about $55 more for the RA1s than the above combo. But I would recommend them being heat cycled.
The DZ II do not heat cycling. And the tread difference is 9/32 for the DZ II, and RA1 is 6/32 and each RA1 weighs 1 lb more than the 215 and 265 DZII but also 1 lb less than the DZII 235 and 275. The section width for
similar sizes are 1/10" smaller for DZ II ay 9.5 front and 10.8 for the rear vs 9.6 and 10.9 for RA1s - but remember these are brand specific reported measurements.
Edit 2: Check this
comparison between RA1 and R888 where the R888 seems to fit our needs better wrt to steering and braking! Yet the RA1 is more expensive. I have not had good servcie with AIM - they gauged my wheels.