@Override
  public <CT, VT extends CT> PdxWriter writeField(String fieldName, VT fieldValue,
      Class<CT> fieldType) {
    return writeField(fieldName, fieldValue, fieldType, false);
  }
Make sure we have room to add a VLF offset.
geode-core/src/main/java/org/apache/geode/pdx/internal/PdxWriterImpl.java