JPanel used for graphics

I'm trying to adapt some existing programs to use Swixml.   Most of the 
conversion is pretty straightfoward, but I'm not sure about the approach to 
use for a JPanel used for graphics -- specifically a panel where 
paintComponent() is overridden. 

It appears that the way to do this is to register a new tag for this 
subclass of JPanel that I've defined.  Is this the correct approach? 

This got me to thinking about other approaches.  The Swix engine could check 
to see if a variable to which a tag is bound already has a non-null value.  
If it's null, then it should create a new instance as it does now.  If it's 
non-null and it's an instance of the appropriate type, then the xml 
attributes should be applied to the existing value.  I'm not sure whether 
it's an easy solution to any other problems, but it would be a simple 
solution to my subclassing problem. 

I'd appreciate it if someone could just give me a quick conformation or 
correction to the question of whether my subclassed JPanel is best 
implemented by registering a new tag. 

Thanks,  Fred