I agree Chris,
I think if we cut the current numbers down to a rectangle within the circular sticker they become a more sensible size, and still readable, so cutting (to a determined minimum size) should be allowed.
I also think the placement should not be over the windows, perhaps centre of wing and one on each side of the shell?
Fair enough, sponsors want the stickers there, but we could soon adapt our sponsor sticker placement to be suitable too?
So many of us now have our own colours, that the refs know who the car belongs to before the number is seen. The only confusing time is when somebody other than Jonesy has an Orange shell...
