I have mentioned assuming there is lot activity on the database as logfiles are small and will be filled so quickly, to avoid the redo creation during the time new log groups are created. Be careful, if you are doing while the database open for users.

Make sure, you switch the logfile to the log group you create with diffrent size before attempting to drop the existing log groups and see all of the log groups you created havng status are inactive/current but not 'unused'.