Hi,
Whether you can get the Stimulsoft control into the Visual Studio toolbox to be able to add it to a ASP.NET web usercontrol does not depend on Visual WebGui.
Just to make everything clear, then you create a Web User Control for that purpose, not a Visual WebGui UserControl. Editing that Web User Control and still unable to add the Stimulsoft component into the toolbox, then there is something missing with regards to Stimulsoft and the Visual Studio you are using. Nothing that should be affected by Visual WebGui there.
If you wish, you can create a new project of type ASP.NET Web Application, add a Web UserControl to it and then try to get it into the toolbox. If you can, you can use the markup code generated there for your wrapped control in your Visual WebGui application.
Palli