Had mine checked this morning, and is set at 1.2°CA. This might possibly be slightly retarded, so does anyone know what the best setting is, and method of adjustment? Or would you be happy to leave it where it is. Also what realistic effect would it have on the overall running if I were to advance it a bit?

Thanks in advance......

I set it so that is advanced as I can manage whilst it is still within limits and this is the correct setting. The basic setting becomes more retarded as the belt ages (stretches). If you set it so that it is retarded (or neutral) when the belt is new, the adaption will not fully correct the timing when approaching the belt end of life.