You are correct -- secondary YAxis cannot be set up through the wizard and you need to either customize it from code or from the property grid.
As for the property grid issues -- recently our developers were able to track and fix problems with changing values from the property grid that are similar to your observations. The fix will be included in the official service pack release that is due by the end of the week.
Sorry for the temporary inconvenience.
the Telerik team
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