I used to use an iframe in edge with other content (usually client made) in and set the edge stage to be the same ratio, with Centre stage and Responsive scaling set to "both". This way I could put the project into mobile pages and edge would do all the scaling perfectly. I know it's a bit hacky butit's the best way I found to do this quickly without re-writing clients code from scratch.
But recently I've tried this and although the project scales great with height the width no longer scales and instead when the width of the window is lowered the height scales UP and the width remains unchanged.
A little more information. I've set my stage to be 1024 x 768, and added rectangle the full size of the stage (named "frame") with the following on creationcomplete:
sym.$('frame').html("<iframe src = 'my content' style = 'width:100%;height:100%;background-color:rgba(0,0,0,0)'></iframe>");
Now the content scales with width's above 980 pixels but below that the width of the content remains the same but the height escalates.
When publishing with responsive scaling make sure you have both selected for height and width.
Responsive AND cetred content is set to both already.