QR3: Switching modeless reports on custom preview = crash

I would like to know if anyone can point me in the direction of a
working "how-to" implementing a custom preview form where one might
change from one report to another without closing down the form. Using
what passes for documentation in QR3, it seems that the previous report
is not cleanly exited before the next preview is executed, leading to
crashes after viewing several reports in sequence. (We have a treeview
with lots of reports that can be clicked to view each report.)

If I understand the Qusoft pages correctly, this should be one of the
'new and improved' things in QR3. Problem is, I can't find any info
anywhere on this new functionality or how to use it...

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Eivind Bakkestuen was here
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"I was the second gunman
 on the grassy knoll."