I agree, I have 8 x 6 on a few bikes and never been stopped or questioned, here or anywhere actually (even in Wales!) but they don't look ridiculously small as only an inch under regs. My 1972 XS has black and white (hand painted it seems!) and never been asked about it. Probably the main reason is that I very rarely see any coppers out on the roads these days, certainly the more rural ones.