This functionality is due to the increased Driver Security implemented with all the new drivers.  When you manually create a 2nd driver instance the CitectSCADA "Driver Security" reports that this 2nd Driver instance is an “experimental” Driver that CitectSCADA is trying to access. As a workaround in v7.0 and higher, you can simply create a second cluster and IOServer instance and configure your additional Driver requirements for this instance of the driver.  This workaround is not available pre CitectSCADA v7.0.  Citect Support suggests that the project is upgraded to v7.0.

The other easy option is the Modnet driver in V7 support port level configuration for some of the ini parameters. Please refer to the KB article Q5141 for more details on which parameter supports the port level configuration.