Mixing different load rating tyres?

[munchkincoupe]

I've got Conti Sport Contact 3 tyres fitted - pair of 92W on the rears and had a pair of 92Y on the fronts. One of the front ones has an unrepairable puncture and they are all on 6-7mm tread

I've been offered a good deal on a used tyre on 6mm across full face, exactly the same except 92W instead of 92Y. Is there really any problem in having a 92Y and a 92W on the fronts?

Thanks for your advice