For a piping or tubing part, include one configuration for each size and specification that you need. To create your own pipe or tube part, copy a SOLIDWORKS sample part to the library folder and give it a unique name. Then edit the design table to create the configurations you need. The length attribute is not used.
For better performance, create several different elbows, rather than creating configurations for all sizes, angles, and class radii in a single elbow part.
Reduce file size by deleting part configurations that you no longer need.