Shallow cups?

[Java]

I'm still pretty new to this whole thing, so I'm wondering; I've read in several threads where a poster will mention a kendama having cups that are too shallow. Pardon my abysmal ignorance, but doesn't the dama rest on the rim of the cup? If so, I don't understand why the depth of the cup makes a difference, as long as it is deep enough to allow for the dama to rest on the rim. What am I missing ?

[The Void]

I'm also confused by this complaint. As long as the radius of the cup is not larger than the radius of the ball, it should be fine.
Of course, maybe that *is* the case in some instances, but that would be a pretty shoddy kendama...

[CDFraser9]

The only time cup depth makes a difference is when the cup is too shallow; meaning the middle of the cup is more on the ball than the rims. It is a rare defect though.