Abstract: A disclosed method of downhole tool system development comprises: receiving specifications of a downhole tool system that comprises multiple strings, each string having one or more components; and checking for interference between the multiple strings in an initial position. A disclosed system comprises: a memory that stores software; and a processor coupled to the memory to execute the software. The software causes the processor to provide a graphical user interface that enables a user to specify a downhole tool system having multiple strings, and to test the strings for diametrical overlap attributable to relative motion of the strings.