I haven't really tested it, but I've seen the following code  using
"SaveProperties = true"

Here's an example:

// Event handler for _mybutton control that sets the
// Title property  to the value in _mytextbox control.
public void _mybutton_click (object sender, EventArgs e)
{
this.Title = _mytextbox.Value;
try
{
this.SaveProperties=true;
}
catch
{
Caption = "Error... Could not save property.";
}
}

I'll give this a shot and provide feedback to the group.

I have tested this quite extensively, and it does work, within limits. I suspect that it only works  for XML sieralizable properties. I tested it with integers, strings, and a custom  class. The string and integer worked perfectly (so I can now fix my Yachted web  part!) but the custom class did not. I’m currently looking into how to make a custom class be sieralizable so it too can be saved as a property.