Have you seen the built-in Visual Modeler mentioned by Deanna here ?
If you haven’t tried it yet: Add-ons menu in VB6, Add-ons Manager. Install Run / Download for the add-in for the add-in for visual modeling and visual modeling. Then in the add-in menu, you should see Visual Modeler ==> Reverse Engineering Wizard.
This was good enough for the chart classes in our (large) project.