It does appear that I was incorrect in asserting that you could add a custom control under the 'Ownership and access rights' section. As you mentioned, it is not even in the documentation and with the 3 controls in that section being flydowns I do not believe you can use them as reference points for adding a new control.
So it might be simplest to define a new section on that tab and add the custom control you want to add to that new section using the name you set for the section as the RelativePositionTo value. You could then use the last control referenced as 'LastLoggedOn' as your control to use for positioning.
