I made a file which includes the ability to switch between the aspect ratios "Windowed", "4:3" and "16:9".
The aspect ratios works pixel-perfect on my computer and monitor.
However, a problem came up when I added "Transitions" in the frames.
When I run the program in "Windowed" both the "Fade In" and "Fade Out" works as they should.
When I run the program in "4:3" or "16:9" only the "Fade Out" work as it completely skips out the "Fade In".
Did you try the "Create before frame fade-in transition" setting?
ChrisD> Employer: Say, wanna see a magic trick?
ChrisD> Employee: Uhh… sure, boss.
ChrisD> Employer: Your job! It just disappeared! Pack your things and leave! Pretty good trick, huh?