InfoPath Dev

Any idea what is the appropriate way to remove a signature programatically?

Using the following code I can remove a signature. Dim xnDoc As XPathNavigator = MainDataSource.CreateNavigator() If (Me.Signed) Then 'unsign it         Dim xSignedSection As XPathNavigator = xnDoc.SelectSingleNode("my:meineFelder/my:signaturen1/my:signaturen2", ...

Everytime when a form is signed infopath writes a screendump in the xml file of the form. This adds 400KB to the xml file with every signature. Is there an option to deactivate this automatical screendump?