Linking testcase to existing requirements in RM

I need to create testcases and link them to existing requirements in RM Server using RQMExcelImporter. I know that there is an option to select the checkbox Link to Existing RM requirement. Is there any alternative for that like give the urn in the column of excel and use either Link or LinkExisting method to link new created testcase to existing requirement?

If I use the option of Link to Existing RM Requirement there is a limitation that if the number of requirements goes beyond 500 timeout happens. Could you provide me better solution?