I guess I could try to source two more rear OEMs to make a square set but according to this website http://felgenkatalog.auto-treff.com/
a rear OEM 219 wheel weighs 12.6 kg or 27 lbs. Apex claims that the Arc 8 18x10 weighs around 19 lbs, and it's 1/2 inch wider. I prefer the look of the OEM wheel but if I can save around 8 lbs of unsprung weight per corner it's a no brainer. I'll go the with Apex.