Hi mate,
I just put the same wheels on. Im just having the same thoughts. After chatting to si, rob.d etc... im going for 40mm. Rob.d says his is fine with 3 people in the back and full ICE. The standard abarth/fiat ones don't drop the car enough cos they are 30mm and 20mm.
Hope that helps.. Let me know what you do cos im not doing mine till next month.
Mr Al.