New TopComponent kind? (in addition to editor and viewer)

I'm developing an application on top of the Netbeans platform. Are
there any ways to replace/customize the editor style TopComponent?

I need a component that occupies the middle part of the window (like
the "editor" kind), but the component should not be closeable and
there should only be one instance of it (allways opened).

I know this can be acheived by having an editor component that is not
closeable, but the close button will still appear, and the tabs and
all the UI stuff for cycling through the oher editor components that
are visible (in my case none). I need a clean component without any of
this, preferrably even without a title.

Can anyone give me a pointer to where to start? E.g. what code/module
to modify etc.