The AutoScale function has changed since B4A version 3.20.
It supports now other screens than the standard one.
What AutoScaleRate did you use.
For downscaling you shoud use an AutoScaleRate equal or near to 1.
You might have a problem with the two screen resolutions you are speaking of due to the much bigger width/height ratio for the 600x1200 screen 1x2 against 1x1.6. The Anchor function will be helpful.
Are you sure that it's 600x1200, it's the first time I see a width/height ratio of 1x2 ?
With AutoScale the scaling would be too streched in one direction but not enough in the other.
You may have a look at following chapters in the Beginner's Guide.
8.9 Designer Scripts
8.10 Anchors
8.11 AutoScale
8.12 UI Cloud
You could also have a look at the
AutoScale Code Module.