My problem was: "He has an ALREADY EXISTING JTable object in his form and needs
to replace this with an instance of his new derived MyJTable class. Is
there any way to achieve this? Deleting the existing JTable object and
re-inserting a MyJTable would work, but all the settings for the old
JTable would be lost."

Workaround:

"Chuck - you are right the IDE does not support such substitution of components.
But it is a feature that could be implemented. Could somebody of you guys file
an enhancement request for 'form' component?

For Harri: in the current state the easiest way is probably to open the .form
file in an external editor and replace "javax.swing.JTable" with your component
class name. Just be careful - do this when the form is not opened in the IDE,
and be sure it is really a subclass of JTable. And note this is just a
workaround - it is generally not recommended to do anything to the .form file.

  - Tomas"