The Visual C Class Wizard, particularly versions prior to VC6, does not produce a proper stub for properties marked as hidden. TatukGIS provides manually altered classes. To use these in your VC program, include the TatukGIS_DK.h header. This will enable access to the IXGIS_xxx classes.
Please do not use the standard generated class for XGIS_ViewerWND that is placed inside the dialog box. Instead, replace the generated class with XGIS_ViewerWND.pas and XGIS_ViewerWND.h.
Also please carefully study the DK-ActiveX Visual C samples provided by TatukGIS.