Ok, here's how to calculate the zoomOutPerc automatically.

These changes go in the ZoomViewer.as file. Place this code before the line:

gmcViewArea.setZoomOutPerc(zoomOutPerc);

And after the line:
var zoomOutPerc = Number(gXMLRoot.attributes.zoomOutPerc);

In my code I set a new variable called _global.maxImageRotation (which is the same as the maxRot constant in the Image.as variable--this defaults to 10.)

If the zoomOutPerc attribute isn't supplied, then it'll calculate the best percentage to use based on the width/height of the stage and the ViewArea.

        // if the zoom out percentage was supplied, calculate it out by ViewArea
        if( isNaN(zoomOutPerc) ){
            // get the maximum rotation percentage
            var iMaxRotation =  _global.maxImageRotation/100;
            // calculate the maximum width percentage
            // Stage Width / (ViewArea Width + (ViewArea Width * Maximum Rotation) )
            var iWidthPerc = Math.floor((_global.sWidth/(gmcViewArea.width + (gmcViewArea.width * iMaxRotation))) * 100);
            // calculate the maximum height percentage
            // Stage Height / (ViewArea Height + (ViewArea Height * Maximum Rotation) )
            var iHeightPerc = Math.floor((_global.sHeight/(gmcViewArea.height + (gmcViewArea.height * iMaxRotation))) * 100);
            // use which ever percentage is smaller--this guarantees all portions
            // of images are displayed
            zoomOutPerc = (iHeightPerc < iWidthPerc) ? iHeightPerc : iWidthPerc;
        }

I'll be working on the zoomInPerc later. Same idea, just need to grab the max image width/height.

-Dan