Although bob_buzzard is absolutely right about the iframe being masked, I have been using the following technique which works for my needs.

I have a "preview" Vf page defined to be displayed as the Mobile Card and set it to a 100px height from the Page Layout. This contains just an icon and some preview text in my case. At the bottom of this preview page I have some JavaScript checking the window height. If the window is greater than the 100px I defined for the Mobile Card, then I redirect to my second Vf page containing my intended functionality.

When you first swipe to view the Mobile Card this JavaScript does nothing because it's confined to the 100px height. When you click on the prevew it will open the page in full screen and then automatically redirect to the second page since the height is now greater than 100px. This results in a quick flash of the preview page, but this is acceptable for me instead of needing to do a second click for navigation. 

So at the bottom of my preview page I used the following:

<script>
    function checkSize() {
        var myHeight = 0;
       
        if( typeof(window.innerHeight) == 'number'  ) {
            myHeight = window.innerHeight;
        }
       
        if( myHeight > 100 ) {
            sforce.one.navigateToURL('/apex/someValidPageName');
        }
    }
    checkSize();
</script>

I appreciate any input on the pros/cons of this method, but so far I have been using it without an issue.