Make TestMovie Swf previews Retain Proper Aspect Ratio and Size?

Laletly I've been creating animations at different aspect ratios and resolutions for social media posts.

The problem is, whenever I test preview the animation with the Ctrl+Enter "TestMovie" shortcut, the swf preview window that pops up is not the same aspect ratio of my actual animation and I have to resize it every time I close it and re-run the TestMovie shortcut.

I also work with a 1920x1080 external monitor that I like to preview the animations on, but when I test 4K animations I have to scale down the preview window down everytime. 

I undertstand it is possible to just adjust the preview window and leave it open and looping on my second monitor so that any new TestMovie previews play at the right size and ascpect ratio, but it is distracting as the animation keeps looping and replaying the audio. Even turning off the "Play" and "Loop" options for the preview window doesn't stop some symbol animations from what I've experienced.

I'm also aware you can dock the swf preview window in the Stage panel area of Adobe Animate, but it doesn't retain the correct aspect ratio nor can it be played from a external monitor. I could also make safe borders on another layer to define what will actually be exported but that doesn't remove the need to resize the preview window if the animation is larger than the monitor it's playing on. 

So I'm wondering if there's any other preview alternatives that are just as quick as using the TestMovie shortcut or any way to make the TestMovie preview window remember its size and aspect ratio each time it is closed and re-opened on an external monitor.

Many thanks for sharing any solutions or animation preview workflows that work well for you!