flicker and wierd resize problems ...

I am experimenting with transitions and came across some wierd problems.
Problems:

With Qt-4.3.x there is flicker when the widget is closed (rather deleted because of the DeleteOnClose Flag.)
Using Qt-4.4.0 there is no flicker (probably due to the use of alien widgets) but there is a wierd resize issue that doesn't come up with Qt-4.3.x. If I start an animation, then resize the widget and start the animation again, the widget jumps back to it's initial size. This doesn't happen with Qt-4.3 and also doesn't happen with Qt-4.4.0 when Keeping the widget alive and showing/hiding it instead of deleting it but I wonder why this can't be achieved with the former approach. (you can try that by commenting out the line setAttribute(Qt::WA_DeleteOnClose, true); in the code below.)
The Performance of the transition is severly affected when the widget's size becomes larger. How can I increase the performance?
Using QGLWidget instead QWidget as baseclass for the Transition class results in flicker when the widget is closed regardless of the version of Qt used. This also happens when the widget is only hidden instead of deleted (upon closing).
Is the difference in behaviour between Qt-4.3 and Qt-4.4 a bug in Qt? Should I file a bug report?

Here is the code (I know it's a little large but the only interesting class is TestTransition and the rest is not really relevant):
Attachment 2207

Thanks in advance
momesana