docs: @Override
      int guessFluffedDataSize() {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(this, tc, "guessFluffedDataSize");
  
          // If the data has been set in 'unserialized' then it will be ignored in these
          // calculations. This seems reasonable, as effectively it still 'belongs' to
          // the App unless/until it is serialized.
  
          int total = 0;
  
          // Add the estimate for the fluffed payload size
          // If the body's JMF message is already fluffed up & cached, ask it for the size.
          // However, it's in a serialized form, so apply our deserialization multiplier.
          // Do NOT hold on to this JSMsgPart, as it could lose validity at any time.
          JsMsgPart part = getPayloadIfFluffed();
          if (part != null) {
              total += part.estimateFieldValueSize(JmsObjectBodyAccess.BODY_DATA_VALUE) * DESERIALIZATION_MULTIPLIER;
          }
  
          // If the JMF message hasn't been fluffed up, find the total assembled length of
          // the payload message if possible.
          else {
              // If we have a valid length, remove a bit & assume the rest is the serialized Object.
              // We don't have a clue what it is, so we'll apply our deserialization multiplier as usual.
              int payloadSize = jmo.getPayloadPart().getAssembledLengthIfKnown();
              if (payloadSize != -1) {
                  total += (payloadSize - FLATTENED_PAYLOAD_PART) * DESERIALIZATION_MULTIPLIER;
              }
              // If the payloadSize == -1, then the body message must have been fluffed up
              // but not yet cached, so we'll locate & cache it now.
              else {
                  // However, it's in a serialized form, so apply our deserialization multiplier.
                  total += getPayload().estimateFieldValueSize(JmsObjectBodyAccess.BODY_DATA_VALUE) * DESERIALIZATION_MULTIPLIER;
              }
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(this, tc, "guessFluffedDataSize", total);
          return total;
      }