diff --git a/address.go b/address.go
index 008e918..3133402 100644
--- a/address.go
+++ b/address.go
@@ -127,7 +127,7 @@ func (aa *ArtAddress) UnmarshalBinary(data []byte) error {
 }
 
 func (aa *ArtAddress) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+99)
+	data := make([]byte, 12+95)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpAddress)
 	data[10] = 0
diff --git a/command.go b/command.go
index 74dbcd9..6d67ef3 100644
--- a/command.go
+++ b/command.go
@@ -51,7 +51,7 @@ func (ac *ArtCommand) UnmarshalBinary(data []byte) error {
 }
 
 func (ac *ArtCommand) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+8)
+	data := make([]byte, 12+4+len(ac.Data))
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpCommand)
 	data[10] = 0
@@ -62,6 +62,6 @@ func (ac *ArtCommand) MarshalBinary() ([]byte, error) {
 		return nil, errors.New("data length must be less than or equal to 512 bytes")
 	}
 	binary.BigEndian.PutUint16(data[14:16], dataLength)
-	data = append(data, ac.Data...)
+	copy(data[16:], ac.Data)
 	return data, nil
 }
diff --git a/datarequest.go b/datarequest.go
index 73e19d4..f179ac2 100644
--- a/datarequest.go
+++ b/datarequest.go
@@ -52,7 +52,7 @@ func (adr *ArtDataRequest) UnmarshalBinary(data []byte) error {
 }
 
 func (adr *ArtDataRequest) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+32)
+	data := make([]byte, 12+28)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpDataRequest)
 	data[10] = 0
diff --git a/diagdata.go b/diagdata.go
index 317fff5..c441ebe 100644
--- a/diagdata.go
+++ b/diagdata.go
@@ -59,7 +59,7 @@ func (add *ArtDiagData) UnmarshalBinary(data []byte) error {
 }
 
 func (add *ArtDiagData) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+10)
+	data := make([]byte, 12+6+len(add.Data))
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpDiagData)
 	data[10] = 0
@@ -73,6 +73,6 @@ func (add *ArtDiagData) MarshalBinary() ([]byte, error) {
 		return nil, errors.New("data length must be less than or equal to 512 bytes")
 	}
 	binary.BigEndian.PutUint16(data[16:18], dataLength)
-	data = append(data, add.Data...)
+	copy(data[18:], add.Data)
 	return data, nil
 }
diff --git a/dmx.go b/dmx.go
index 6b81d7d..276ee38 100644
--- a/dmx.go
+++ b/dmx.go
@@ -54,7 +54,7 @@ func (ad *ArtDmx) UnmarshalBinary(data []byte) error {
 
 func (ad *ArtDmx) MarshalBinary() ([]byte, error) {
 	// TODO(jwetzell): check max data length
-	data := make([]byte, 8+10+len(ad.Data))
+	data := make([]byte, 12+6+len(ad.Data))
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpDmx)
 	data[10] = 0
diff --git a/ipprog.go b/ipprog.go
index cff1526..3f140b1 100644
--- a/ipprog.go
+++ b/ipprog.go
@@ -83,7 +83,7 @@ func (aip *ArtIpProg) UnmarshalBinary(data []byte) error {
 }
 
 func (aip *ArtIpProg) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+26)
+	data := make([]byte, 12+22)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpIpProg)
 	data[10] = 0
diff --git a/ipprogreply.go b/ipprogreply.go
index 84dc810..ba22873 100644
--- a/ipprogreply.go
+++ b/ipprogreply.go
@@ -84,7 +84,7 @@ func (aipr *ArtIpProgReply) UnmarshalBinary(data []byte) error {
 }
 
 func (aipr *ArtIpProgReply) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+26)
+	data := make([]byte, 12+22)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpIpProgReply)
 	data[10] = 0
diff --git a/nzs.go b/nzs.go
index 2b0423b..dd44e82 100644
--- a/nzs.go
+++ b/nzs.go
@@ -50,7 +50,7 @@ func (an *ArtNzs) UnmarshalBinary(data []byte) error {
 }
 
 func (an *ArtNzs) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+8)
+	data := make([]byte, 12+6+len(an.Data))
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpNzs)
 	data[10] = 0
diff --git a/poll.go b/poll.go
index f99b1e1..ac0e186 100644
--- a/poll.go
+++ b/poll.go
@@ -55,7 +55,7 @@ func (ap *ArtPoll) UnmarshalBinary(data []byte) error {
 }
 
 func (ap *ArtPoll) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+14)
+	data := make([]byte, 12+10)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpPoll)
 	data[10] = 0
diff --git a/pollreply.go b/pollreply.go
index 559bf28..6718582 100644
--- a/pollreply.go
+++ b/pollreply.go
@@ -28,9 +28,9 @@ type ArtPollReply struct {
 	AcnPriority uint8
 	SwMacro     uint8
 	SwRemote    uint8
-	Spare1      uint8
-	Spare2      uint8
-	Spare3      uint8
+	spare1      uint8
+	spare2      uint8
+	spare3      uint8
 	Style       uint8
 	MAC         [6]uint8
 	// TODO(jwetzell): support extended poll fields
@@ -89,9 +89,9 @@ func (ap *ArtPollReply) UnmarshalBinary(data []byte) error {
 	ap.AcnPriority = data[194]
 	ap.SwMacro = data[195]
 	ap.SwRemote = data[196]
-	ap.Spare1 = data[197]
-	ap.Spare2 = data[198]
-	ap.Spare3 = data[199]
+	ap.spare1 = data[197]
+	ap.spare2 = data[198]
+	ap.spare3 = data[199]
 	ap.Style = data[200]
 	copy(ap.MAC[:], data[201:207])
 	return nil
@@ -128,9 +128,9 @@ func (ap *ArtPollReply) MarshalBinary() ([]byte, error) {
 	data[194] = ap.AcnPriority
 	data[195] = ap.SwMacro
 	data[196] = ap.SwRemote
-	data[197] = ap.Spare1
-	data[198] = ap.Spare2
-	data[199] = ap.Spare3
+	data[197] = ap.spare1
+	data[198] = ap.spare2
+	data[199] = ap.spare3
 	data[200] = ap.Style
 	copy(data[201:207], ap.MAC[:])
 	copy(data[207:211], ap.BindIp[:])
diff --git a/sync.go b/sync.go
index 149ba8f..3828123 100644
--- a/sync.go
+++ b/sync.go
@@ -37,7 +37,7 @@ func (as *ArtSync) UnmarshalBinary(data []byte) error {
 }
 
 func (as *ArtSync) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+6)
+	data := make([]byte, 12+2)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpSync)
 	data[10] = 0
diff --git a/timecode.go b/timecode.go
index e2cc13b..d6caf64 100644
--- a/timecode.go
+++ b/timecode.go
@@ -46,7 +46,7 @@ func (atc *ArtTimeCode) UnmarshalBinary(data []byte) error {
 }
 
 func (atc *ArtTimeCode) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+11)
+	data := make([]byte, 12+7)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpTimeCode)
 	data[10] = 0
diff --git a/todcontrol.go b/todcontrol.go
index cdffb2f..b0655b2 100644
--- a/todcontrol.go
+++ b/todcontrol.go
@@ -67,7 +67,7 @@ func (adr *ArtTodControl) UnmarshalBinary(data []byte) error {
 }
 
 func (adr *ArtTodControl) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+16)
+	data := make([]byte, 12+12)
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpTodControl)
 	data[10] = 0
diff --git a/todrequest.go b/todrequest.go
index 89f33d5..4350d3c 100644
--- a/todrequest.go
+++ b/todrequest.go
@@ -71,7 +71,7 @@ func (adr *ArtTodRequest) MarshalBinary() ([]byte, error) {
 	if len(adr.Address) > 32 {
 		return nil, errors.New("address count must not be greater than 32")
 	}
-	data := make([]byte, 8+16+len(adr.Address))
+	data := make([]byte, 12+12+len(adr.Address))
 	copy(data[0:8], ArtNetID[:])
 	binary.LittleEndian.PutUint16(data[8:10], OpTodRequest)
 	data[10] = 0
diff --git a/trigger.go b/trigger.go
index 172a9c4..d07ebc7 100644
--- a/trigger.go
+++ b/trigger.go
@@ -63,7 +63,7 @@ func (at *ArtTrigger) UnmarshalBinary(data []byte) error {
 }
 
 func (at *ArtTrigger) MarshalBinary() ([]byte, error) {
-	data := make([]byte, 8+10)
+	data := make([]byte, 12+6)
 	copy(data[0:8], at.id[:])
 	binary.LittleEndian.PutUint16(data[8:10], at.opCode)
 	data[10] = at.ProtVerHi