Yes, you can have two WSTOMSTC (Tomcat) running on the same LPAR as long as you they are running on different ports and you have enough USS space to install different version of Web Services.
Here is the sample setting for running both WSTOMSTC (for 18 INC00 aka V18.0) and WSTOMSTC2 (for 18 INC12 aka V18.0.12) on the same LPAR
Tomcat (WSTOMSTC) for V18.0 spawn task for V18.0 (WSEWSSTC- steplib and conlib pointing to V18.0 library) spawn parameter file for WSEWSSTC ( CAICCI SERVICE and PROCESS statements in the ndvspawn file) Data Source for spawn task 18.0 (Endevor.cfg - jobName= WSEWSSTC )
Tomcat (WSTOMSTC2) for V18.0.12 (running on different port) spawn task for V18.0.12 (WSEWSTC2, use V18.0.12 steplib and conlib) spawn parameter file for WSEWSTC2 (sample spawn param file - iprfx.iqual.CSIQOPTN(WSEWSCCI)) Data Source for spawn task 18.0.12 (Endevor2.cfg - jobName=WSEWSTC2)