How to disable posting to parent forum (only post to subforms)

[bpabbott]

Octave's maintainers would like to disable new-topics/posts to http://octave.1599824.n4.nabble.com, or just hide this forum ... but continue to allow posts to Octave's two active subforms.

1) Octave : http://octave.1599824.n4.nabble.com
        1.1) Octave - Maintainers : http://octave.1599824.n4.nabble.com/Octave-Maintainers-f1638794.html
        1.2) Octave - General : http://octave.1599824.n4.nabble.com/Octave-General-f1599825.html

What are our options? If we "Change Application Type" to "Mixed" will the subforms remain intact?