Hi Alonso,
There's usually a reason for attributes to be set as 'Read Only' for a specific class. If you actually changed those, it would probably lead to an inconsistency, since 'Radius' is a Dependent variable.
The attributes you mention can only be set by calling the constructor.
Hence, I would recommend creating a new sphereModel object: you may set the Radius to the modified value and use the values from 'model.Bead1' for all other attributes.
Hope it Helps!