The hanging method for copper foiled and leaded panels depends to a large extent on size and weight. The larger and heavier the panel is, the stronger support that is required. Smaller light weight panels are not usually a problem as the solder lines and joints can take the weight. Leaded panels require more support than copper foiled panels once they are over a few kilos, or are anything but rectangular.
For heavier panels you need to have stronger supports than just the perimeter calmes or solder beading.
For rectangular panels you can use a stronger edge came such as zinc or brass. Solder this to each meeting joint throughout the length of the panel. This distributes the hanging stress across the panel more effectively. Simple soldering at the four corners of the calme will rely on just those solder joints to carry the whole weight of the panel.
You need to make the vertical borders of single pieces so that you are not relying on the strength of a single solder joint at some point along the side. Although the joint may be strong enough at present, it must stand up to the weight of the panel over a long period of time.
All this relies on secure attachment of the hanging hooks or wire