Phonegap + Windows Phone 8 : viewport meta & scaling issue

I'm currently working on a Phonegap app and I have the following problem when testing it with Windows Phone 8 (left screenshot below): the application bar is not removed and leaves a big white space.

From various sources I learned that the following meta tag is ignored by WP8:

<meta name="viewport" content="width=device-width, height=device-height">

So you have to define it again using the "ms" pre-tag:

@-ms-viewport {
    height: device-height;
    width: device-width;
}

But doing so kind of messes up with the scaling of the app. Any idea what is going on?

Here the before after screenshot: