Hi!
Prior to the latest beta 12.03 there was a problem with FormStyle set to fsMDIForm. That's gone inte the beta but there's another problem.
If you have a setup with more then one monitor and the different monitors have different Scaling set. Perhaps one att 100% and another at 125%. If you create an MDIChild and maximize it and then restore it the main MDI form will get the old Windows XP boarders.
Tested on Berlin and Tokyo with beta 12.03.
Best regards,
/Pontus