Well, I guess the Basik is a little heavier than I remembered. It's been 20 years since they made that arm.
However, I think that the idea that it is too light for the Grado cartridge is very fishy. I could understand too heavy, but too light sounds strange to me.
If it is in fact too light, then about 98% of all arms are too light for it, because there are very few arms being manufactured that are over 12 grams. I have a hard time swallowing the idea that Grado would make a cartridge that can only be used in so very few arms. The general audio user consensus is that the Grados need a lighter arm, not a heavier one.
It is my estimation that either they didn't communicate well to you, or they made a mistake. However, I don't presume to tell Grado about their cartridges.