I investigated the possibility of cloning menus, and the best I could come up with was to allow an easy way to clone a submenu, but however, there will still be 2 menus defined.
The nice thing though is that you can easily define it with:
<ul id="foo-bar">
... menu contents ...
</ul>
<li class="clones-popup-foo-bar">Foo bar</li>
The above creates an item having the label “Foo bar” and having the submenu defined by the UL with the ID “foo-bar”. You can clone it as many times you want. The UL doesn't even need to be a descendent of the main menu UL--it can be defined anywhere in your document, possibly for other purposes than being a menu. ;-) It's as fast as if you would have one UL for each menu, though—I mean, the menu elements are duplicated. The current architecture of DynarchMenu does not allow simply using references.
I'll release the new code soon and you will be able to upgrade and test it.