An entire project can be made of lead came or another came. If you are going to use zinc, brass or other hard metal to build an entire project, all lines in the design should be straight or angled. Hard metals do not conform to round shaped pieces of glass very well. With larger projects the weight of glass and other materials used in a project must be considered. If you want to err, err on the conservative side by adding plenty of strength to your project.
Many larger projects require some type of reinforcing.
This is true with copper foil and came. In some cases steel, iron, or wood are used as strengtheners in strategic areas of the project. Anything larger than two square feet should be considered for reinforcement. Came requires some different tools and slightly different technique than copper-foil. Tight inside and outside curves on glass are hard to shape around with came, the larger the came size, the tougher it gets.