Not that Im aware of - it handles just fine, and Ive no issue of wear on tyres and or bearings - but Ive probably only done 3-4k since fitting the spacers, and Im no track driver or pedal to the metal everywhere driver, so Im not in a position to judge how the car reacts when pushed to the limits with or without spacers.
If I recall, Big Phill ran 50mm spacers on the rear of his and it never missed a beat, thats what he said to me when I was making spacer enquiries when I was at his garage just over a year ago.