diff --git a/README.md b/README.md
index 86d7737..28cd884 100644
--- a/README.md
+++ b/README.md
@@ -14,10 +14,18 @@ import "go.ajitem.com/zapdriver"
 This package provides three building blocks to support the full array of
 structured logging capabilities of Stackdriver:
 
-* [Special purpose logging fields](#special-purpose-logging-fields)
-* [Pre-configured Stackdriver-optimized encoder](#pre-configured-stackdriver-optimized-encoder)
-* [Custom Stackdriver Zap core](#custom-stackdriver-zap-core)
-* [Using Error Reporting](#using-error-reporting)
+- [:zap: Zapdriver](#zap-zapdriver)
+  - [Usage](#usage)
+    - [Special purpose logging fields](#special-purpose-logging-fields)
+      - [HTTP](#http)
+      - [Label](#label)
+      - [SourceLocation](#sourcelocation)
+      - [Operation](#operation)
+      - [TraceContext](#tracecontext)
+    - [Pre-configured Stackdriver-optimized encoder](#pre-configured-stackdriver-optimized-encoder)
+    - [Custom Stackdriver Zap core](#custom-stackdriver-zap-core)
+    - [Using Error Reporting](#using-error-reporting)
+      - [Reporting errors manually](#reporting-errors-manually)
 
 The above components can be used separately, but to start, you can create a new
 Zap logger with all of the above included:
@@ -93,7 +101,7 @@ one or the other will be omitted if `nil` is passed in.
 Note that there are some fields that are not populated by either the request or
 response object, and need to be set manually:
 
-* `ServerIP string`
+
 * `Latency string`
 * `CacheLookup bool`
 * `CacheHit bool`
diff --git a/http.go b/http.go
index 441e585..b5d294f 100644
--- a/http.go
+++ b/http.go
@@ -117,24 +117,49 @@ func NewHTTP(req *http.Request, res *http.Response) *HTTPPayload {
 		RemoteIP:      req.RemoteAddr,
 		Referer:       req.Referer(),
 		Protocol:      req.Proto,
+		ServerIP:      req.Host,
 	}
 
 	if req.URL != nil {
 		sdreq.RequestURL = req.URL.String()
 	}
 
+	// Count the requestSize: both headers and body
+	var requestSize int64
+
+	for hKey, hValue := range req.Header {
+		requestSize += int64(len([]byte(hKey)))
+		for _, v := range hValue {
+			requestSize += int64(len([]byte(v)))
+		}
+	}
+
 	buf := &bytes.Buffer{}
 	if req.Body != nil {
 		n, _ := io.Copy(buf, req.Body) // nolint: gas
-		sdreq.RequestSize = strconv.FormatInt(n, 10)
+		requestSize += n
+	}
+
+	sdreq.RequestSize = strconv.FormatInt(requestSize, 10)
+
+	// Count the response size, both headers and body
+	var responseSize int64
+
+	for hKey, hValue := range res.Header {
+		responseSize += int64(len([]byte(hKey)))
+		for _, v := range hValue {
+			responseSize += int64(len([]byte(v)))
+		}
 	}
 
 	if res.Body != nil {
 		buf.Reset()
 		n, _ := io.Copy(buf, res.Body) // nolint: gas
-		sdreq.ResponseSize = strconv.FormatInt(n, 10)
+		responseSize += n
 	}
 
+	sdreq.ResponseSize = strconv.FormatInt(responseSize, 10)
+
 	return sdreq
 }
 
@@ -142,8 +167,8 @@ func NewHTTP(req *http.Request, res *http.Response) *HTTPPayload {
 func (req HTTPPayload) MarshalLogObject(enc zapcore.ObjectEncoder) error {
 	enc.AddString("requestMethod", req.RequestMethod)
 	enc.AddString("requestUrl", req.RequestURL)
-	enc.AddString("requestSize", req.RequestSize)
 	enc.AddInt("status", req.Status)
+	enc.AddString("requestSize", req.RequestSize)
 	enc.AddString("responseSize", req.ResponseSize)
 	enc.AddString("userAgent", req.UserAgent)
 	enc.AddString("remoteIp", req.RemoteIP)
@@ -153,8 +178,11 @@ func (req HTTPPayload) MarshalLogObject(enc zapcore.ObjectEncoder) error {
 	enc.AddBool("cacheLookup", req.CacheLookup)
 	enc.AddBool("cacheHit", req.CacheHit)
 	enc.AddBool("cacheValidatedWithOriginServer", req.CacheValidatedWithOriginServer)
-	enc.AddString("cacheFillBytes", req.CacheFillBytes)
 	enc.AddString("protocol", req.Protocol)
 
+	if req.CacheFillBytes != "" {
+		enc.AddString("cacheFillBytes", req.CacheFillBytes)
+	}
+
 	return nil
 }
diff --git a/http_test.go b/http_test.go
index 42aa1cb..ebc6938 100644
--- a/http_test.go
+++ b/http_test.go
@@ -35,61 +35,61 @@ func TestNewHTTP(t *testing.T) {
 		"empty": {
 			nil,
 			nil,
-			&zapdriver.HTTPPayload{},
+			&zapdriver.HTTPPayload{RequestSize: "0", ResponseSize: "0"},
 		},
 
 		"RequestMethod": {
 			&http.Request{Method: "GET"},
 			nil,
-			&zapdriver.HTTPPayload{RequestMethod: "GET"},
+			&zapdriver.HTTPPayload{RequestMethod: "GET", RequestSize: "0", ResponseSize: "0"},
 		},
 
 		"Status": {
 			nil,
 			&http.Response{StatusCode: 404},
-			&zapdriver.HTTPPayload{Status: 404},
+			&zapdriver.HTTPPayload{Status: 404, RequestSize: "0", ResponseSize: "0"},
 		},
 
 		"UserAgent": {
 			&http.Request{Header: http.Header{"User-Agent": []string{"hello world"}}},
 			nil,
-			&zapdriver.HTTPPayload{UserAgent: "hello world"},
+			&zapdriver.HTTPPayload{UserAgent: "hello world", RequestSize: "21", ResponseSize: "0"},
 		},
 
 		"RemoteIP": {
 			&http.Request{RemoteAddr: "127.0.0.1"},
 			nil,
-			&zapdriver.HTTPPayload{RemoteIP: "127.0.0.1"},
+			&zapdriver.HTTPPayload{RemoteIP: "127.0.0.1", RequestSize: "0", ResponseSize: "0"},
 		},
 
 		"Referrer": {
 			&http.Request{Header: http.Header{"Referer": []string{"hello universe"}}},
 			nil,
-			&zapdriver.HTTPPayload{Referer: "hello universe"},
+			&zapdriver.HTTPPayload{Referer: "hello universe", RequestSize: "21", ResponseSize: "0"},
 		},
 
 		"Protocol": {
 			&http.Request{Proto: "HTTP/1.1"},
 			nil,
-			&zapdriver.HTTPPayload{Protocol: "HTTP/1.1"},
+			&zapdriver.HTTPPayload{Protocol: "HTTP/1.1", RequestSize: "0", ResponseSize: "0"},
 		},
 
 		"RequestURL": {
 			&http.Request{URL: &url.URL{Host: "example.com", Scheme: "https"}},
 			nil,
-			&zapdriver.HTTPPayload{RequestURL: "https://example.com"},
+			&zapdriver.HTTPPayload{RequestURL: "https://example.com", RequestSize: "0", ResponseSize: "0"},
 		},
 
 		"RequestSize": {
 			&http.Request{Body: ioutil.NopCloser(strings.NewReader("12345"))},
 			nil,
-			&zapdriver.HTTPPayload{RequestSize: "5"},
+			&zapdriver.HTTPPayload{RequestSize: "5", ResponseSize: "0"},
 		},
 
 		"ResponseSize": {
 			nil,
 			&http.Response{Body: ioutil.NopCloser(strings.NewReader("12345"))},
-			&zapdriver.HTTPPayload{ResponseSize: "5"},
+			&zapdriver.HTTPPayload{ResponseSize: "5", RequestSize: "0"},
 		},
 
 		"simple request": {
@@ -101,19 +101,21 @@ func TestNewHTTP(t *testing.T) {
 				RemoteIP:      "192.0.2.1:1234",
 				Protocol:      "HTTP/1.1",
 				RequestURL:    "/",
+				ResponseSize:  "0",
+				ServerIP:      "example.com",
 			},
 		},
 
 		"simple response": {
 			nil,
 			&http.Response{Body: ioutil.NopCloser(strings.NewReader("12345")), StatusCode: 404},
-			&zapdriver.HTTPPayload{ResponseSize: "5", Status: 404},
+			&zapdriver.HTTPPayload{RequestSize: "0", ResponseSize: "5", Status: 404},
 		},
 
 		"request & response": {
 			&http.Request{Method: "POST", Proto: "HTTP/1.1"},
 			&http.Response{StatusCode: 200},
-			&zapdriver.HTTPPayload{RequestMethod: "POST", Protocol: "HTTP/1.1", Status: 200},
+			&zapdriver.HTTPPayload{RequestMethod: "POST", Protocol: "HTTP/1.1", Status: 200, RequestSize: "0", ResponseSize: "0"},
 		},
 	}