We apologize for the instability of composr.app and appreciate your patience. We are working on the statistics addon and trying to find an optimal way to store and render data. Unfortunately, we have yet to find a solution that can handle the traffic (and therefore, tens of millions of statistical records) of composr.app. We're working hard on one.
'wide_high' would be used to control how it works in iframes, AJAX results, etc.
All iframes should load with transparency, so the background colour of where the iframe is is used, rather than the iframe's body tag's background.