DotNetZip doesn't close the self extractor form until the post extraction run program closes

Question

I'm using DotNetZip to make a self-extracting archive (SFXtest.exe) which runs a program once extracted (testapp.exe) - the problem I'm having is that the form displayed during the extraction remains showing until testapp.exe closes - ideally I would like the extraction form to close when extraction is complete, just leaving testapp.exe running.

Code example:

       Dim FileList As New List(Of String)
    FileList.Add("c:\test\testapp.exe")
    FileList.Add("c:\test\testdll.dll")

    Dim SFXSaveOptions As New SelfExtractorSaveOptions

    Using zip As New Ionic.Zip.ZipFile
        With SFXSaveOptions
            .DefaultExtractDirectory = Path.GetTempPath
            .ExtractExistingFile = ExtractExistingFileAction.OverwriteSilently
            .Flavor = SelfExtractorFlavor.WinFormsApplication
            .Quiet = True
            .PostExtractCommandLine = "testapp.exe"
            .RemoveUnpackedFilesAfterExecute = False
        End With

        For i = 0 To 1
            zip.UpdateFile(FileList(i), "")
        Next

        zip.SaveSelfExtractor("c:\test\SFXTest.exe", SFXSaveOptions)
    End Using