It seems that the moment you resize or move the popup, ignition assigns a width and height to the element above the popup view.
I dont think there is going to be anything you can do (without javascript) to prevent this.
You could target the popup specificly with a css to unset the width and height.
Resizing with the mouse wont work anymore but dragging still works
#popup-YourPopupId {
width: auto !important;
height: auto !important;
}
