Using modal winforms in OneNote

Hello MS-Office Experts,

I am developing a COM-based OneNote 2013 add-in in c#. As part of the add-in, modal winforms are to be shown. Normally, one would do this along the lines of

OneNote.Window context = control.Context as OneNote.Window;
            CWin32WindowWrapper owner =
                new CWin32WindowWrapper((IntPtr)context.WindowHandle);

MyForm form = new MyForm();
form.ShowDialog(owner);

However, OneNote requires the add-in to be executed inside the DLLSurrogate/dllhost process. This collides with the desired modality of the winform as modality across process boundaries is not meant to be. As a consequence many minor and major issues arise:

+ the winform does not flash when clicking on OneNote (the supposed owner of the winform)

+ the winform looses focus when clicking on OneNote. However, OneNote is still being blocked

+ the add-in hangs when touching OneNote (i.e. touching the multi-touch monitor where OneNote is visible)

Any idea what to do?

I figure that the root cause of the problem is the process boundary. Is it possible to create a custom surrogate that runs inside the OneNote process? Would that solve the problem?

Thank you for your time an effort

Best