Index: src/ooxml/java/org/apache/poi/xssf/streaming/SXSSFWorkbook.java
===================================================================
--- src/ooxml/java/org/apache/poi/xssf/streaming/SXSSFWorkbook.java	(revision 1430930)
+++ src/ooxml/java/org/apache/poi/xssf/streaming/SXSSFWorkbook.java	(working copy)
@@ -99,18 +99,6 @@
      * </ol>
      * All three use cases can work in a combination.
      * </p>
-     * What is not supported:
-     * <ul>
-     *   <li>
-     *   Access initial cells and rows in the template. After constructing
-     *   SXSSFWorkbook(XSSFWorkbook) all internal windows are empty and
-     *   SXSSFSheet@getRow and SXSSFRow#getCell return null.
-     *   </li>
-     *   <li>
-     *    Override existing cells and rows. The API silently allows that but
-     *    the output file is invalid and Excel cannot read it.
-     *   </li>
-     * </ul>
      *
      * @param workbook  the template workbook
      */
Index: src/ooxml/java/org/apache/poi/xssf/streaming/SXSSFSheet.java
===================================================================
--- src/ooxml/java/org/apache/poi/xssf/streaming/SXSSFSheet.java	(revision 1430930)
+++ src/ooxml/java/org/apache/poi/xssf/streaming/SXSSFSheet.java	(working copy)
@@ -155,6 +155,13 @@
      */
     public void removeRow(Row row)
     {
+        // If the row belongs to the template, delete it from the template.
+        if (row.getSheet() == _sh) {        
+            _sh.removeRow(row);
+            return;
+        }
+        
+        // Otherwise try to delete it from the row cache.
         if (row.getSheet() != this) {
             throw new IllegalArgumentException("Specified row does not belong to this sheet");
         }
@@ -179,7 +186,11 @@
      */
     public Row getRow(int rownum)
     {
-        return _rows.get(new Integer(rownum));
+        Row row = _sh.getRow(rownum);
+        if (row == null) {
+            row = _rows.get(new Integer(rownum));
+        }
+        return row;
     }
 
     /**
@@ -189,7 +200,7 @@
      */
     public int getPhysicalNumberOfRows()
     {
-        return _rows.size()+_writer.getNumberOfFlushedRows();
+        return _sh.getPhysicalNumberOfRows() + _rows.size()+_writer.getNumberOfFlushedRows();
     }
 
     /**
@@ -199,9 +210,14 @@
      */
     public int getFirstRowNum()
     {
+        int templateFirst = _sh.getPhysicalNumberOfRows() > 0 ? _sh.getFirstRowNum() : Integer.MAX_VALUE;
+        int newRowsFirst = Integer.MAX_VALUE;
         if(_writer.getNumberOfFlushedRows() > 0)
-            return _writer.getLowestIndexOfFlushedRows();
-        return _rows.size() == 0 ? 0 : _rows.firstKey();
+            newRowsFirst = _writer.getLowestIndexOfFlushedRows();
+        else
+            newRowsFirst = _rows.size() == 0 ? Integer.MAX_VALUE : _rows.firstKey();
+        int first = templateFirst < newRowsFirst ? templateFirst : newRowsFirst;
+        return first == Integer.MAX_VALUE ? 0 : first;
     }
 
     /**
@@ -211,7 +227,9 @@
      */
     public int getLastRowNum()
     {
-        return _rows.size() == 0 ? 0 : _rows.lastKey();
+        int newRowsLast = _rows.size() == 0 ? 0 : _rows.lastKey();
+        int templateLast = _sh.getPhysicalNumberOfRows() > 0 ? _sh.getLastRowNum() : 0;
+        return newRowsLast > templateLast ? newRowsLast : templateLast;
     }
 
     /**
@@ -424,7 +442,9 @@
     }
 
     /**
-     *  Returns an iterator of the physical rows
+     *  Returns an iterator of the physical rows. This will ONLY iterate over those
+     *  cached rows that have not yet been flushed to a temporary file and not over
+     *  rows in the template sheet.
      *
      * @return an iterator of the PHYSICAL rows.  Meaning the 3rd element may not
      * be the third row if say for instance the second row is undefined.
@@ -1096,6 +1116,13 @@
      */
     public void groupRow(int fromRow, int toRow)
     {
+        // Increase the outline level of any template rows first.
+        for (int i = fromRow; i <= toRow; i++){        
+            if (_sh.getRow(i) != null){
+                _sh.groupRow(i,  i);
+            }
+        }
+                
         for(SXSSFRow row : _rows.subMap(fromRow, toRow + 1).values()){
             int level = row.getOutlineLevel() + 1;
             row.setOutlineLevel(level);