Panel/Sizer ?? Sizer question.

Speaking of sizers:

I put Panels in all my Frames at the top level right
under sizer_1. Worked fine except for two windows
in which a tiny panel appeared and you couldn't really see
anything else(on WinXP, worked ok on Kubuntu).
One of those Frames had

  def __set_properties(self):
        # begin wxGlade: PAYF.__set_properties
        self.SetTitle("Receive Payment")
        self.SetSize((500, 500))

I removed the SetSize and let Glade generate code again
and it added to that Frame

       sizer_1.Fit(self)

and now it works fine. Would imply Fit() is important if
you have a panel. Before I added the panels all frames worked ok.

AND THEN, I have one frame which has a Panel and a SetSize()
and does NOT have a Fit(). That one Does work fine on XP.
Aaiiih! ???