Carlo, I do not work for Graham. Get in touch with them and ask about it.
But, after thinking about it a 9 gm Cartridge is not that heavy. It must be a wood body Koetsu. It should balance out so something is wrong with the set up or the way the tonearm was put together. It is a 12" arm which would require a heavier weight than a 9 or 10" arm. Maybe they gave you the wrong weight with the arm accidentally. Also the Koetsu is a very stiff cartridge and that is a lighter tone arm. You will probably have to add some weight to the head shell to get the resonance frequency down or get a stone body Koetsu which is much heavier.
It would look pretty ugly but you could wrap some lead or wheel balance weights around the counter weight for the time being.
But, after thinking about it a 9 gm Cartridge is not that heavy. It must be a wood body Koetsu. It should balance out so something is wrong with the set up or the way the tonearm was put together. It is a 12" arm which would require a heavier weight than a 9 or 10" arm. Maybe they gave you the wrong weight with the arm accidentally. Also the Koetsu is a very stiff cartridge and that is a lighter tone arm. You will probably have to add some weight to the head shell to get the resonance frequency down or get a stone body Koetsu which is much heavier.
It would look pretty ugly but you could wrap some lead or wheel balance weights around the counter weight for the time being.