That's part of the problem.
When I design a scene, I often use images that are larger than the scene itself. That way I can position them around and get the section that I want to show, where I want it. Or sometimes use a dyanmic effect to mover them. But in the webplayer preview, the upper left corner is looking okay, but anything that is bigger than the orignal scene to right, for example, is still shown.
I don't think Iframes would work and they aren't supported by some browsers anymore (I think). I was hoping for something like a youtube embed that you can set the width and height of the embed. That would cut off the undesirable extra right image stuff.