From this, it doesn't appear that you have 100% width/height scaling enabled... at least not on the first scene. The default_hype_container div is showing
"width:800px;height:540px;" and if you did it would show
"width:100%;height:100%;". When this is in effect, then the fact that the scene has
overflow:hidden enabled wouldn't matter, since the scene size would be the whole window size. You may simply need to re-export with the new container sizes?
Otherwise, the unsupported method to do what you ask would be just to override the style via:
overflow: visible !important;
But feel free to elaborate on the issue; it isn't clear to me what you're hitting without the exact .hype doc.