Hi @BrannonKing,
You can change the default rmw implementation by defining the RMW_IMPLEMENTATION environment variable before compiling (you will need to make sure to recompile the rmw_implementation package for the change to take effect).
You can also change the default rmw implementation used by modifying this file.
Setting this variable before compiling only changes which rmw_implementation library will be opened by default. It still compiles all rmw implementation allowing you to select another one at runtime by setting RMW_IMPLEMENTATION if you want to.