Add two copies of a JPanel to a program's main JPanel with Netbeans GUI editor

[Chanbre]

Using the Netbeans design editor I have created a JPanel (as "public class LengthPanel extends javax.swing.JPanel {...}" ) containing a few items. Now I want to place two copies of that panel into the JPanel of the main form of my program. How do I do this? Part of my problem is not knowing the what question to ask of web search engines.

What I really want is a have data entry gadgets for height and width. Each value can be entered as metric (needing one number) or imperial (two numbers) values with its own JComboBox to choose. I want to design and code one length-entry gadget and have two copies of it. It seems easy to make a JPanel to do what I want, but I have not found any discussion of how to make two copies of that panel. Perhaps I should base my gadget on something other that a JPanel; but if so, what?

Using Netbeans 6.9