The .NET 3.0 designer is in its early stages, and probably does not support .NET 2.0 components at this time. Even our WPF DataGrid does not provide any support for the .NET designer, because it is not enough developed. It will come in a subsequent release, as an official release of the .NET designer is released. Moreover, to use .NET 2.0 components at this time in .NET 3.0, you need to use a wrapper panel. You won't be able to use them in one of the regular panels.
André
Software Developer and Tech Support
Xceed Software Inc.