Can I have content larger than 320 pixels in the iPhone using the viewport tag with device width and initial scale = 1?

Question

I am developing a website that I want to feel "appy" for users who will access them via phones, tablets and desktops. I am using jQuery Mobile for this.

For some reason, jQuery mobile requires a viewport tag with a width of width = device-width, initial-scale = 1.

If I choose any other width, any other initial scale, or I delete either, then jQuery mobile behaves terribly badly. (transitions look jerky, things jump up and down, it's terrible).

Now 320px is a bit narrow for my content, and I kind of expected to set the width of the viewport to at least 480 pixels, or maybe more so that things looked “smaller” and still didn't have horizontal scrolling.

Is there any other way to achieve this (basically, being able to place more than 320 pixels of content) while maintaining the viewport tag as jquery mobile?

Thanks!
Daniel