diff --git a/CMakeLists.txt b/CMakeLists.txt
index fa4de1e5..4bb6398b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -45,6 +45,7 @@ add_library(lego1 SHARED
   LEGO1/jukeboxentity.cpp
   LEGO1/jukeboxstate.cpp
   LEGO1/legoact2state.cpp
+  LEGO1/legoactor.cpp
   LEGO1/legoactioncontrolpresenter.cpp
   LEGO1/legoanimactor.cpp
   LEGO1/legoanimationmanager.cpp
diff --git a/LEGO1/islepathactor.cpp b/LEGO1/islepathactor.cpp
index d6386044..0024b4bc 100644
--- a/LEGO1/islepathactor.cpp
+++ b/LEGO1/islepathactor.cpp
@@ -1,5 +1,7 @@
 #include "islepathactor.h"
 
+DECOMP_SIZE_ASSERT(IslePathActor, 0x160)
+
 // OFFSET: LEGO1 0x1001a200
 IslePathActor::IslePathActor()
 {
@@ -12,4 +14,4 @@ IslePathActor::IslePathActor()
 // OFFSET: LEGO1 0x10002e10
 IslePathActor::~IslePathActor()
 {
-}
\ No newline at end of file
+}
diff --git a/LEGO1/islepathactor.h b/LEGO1/islepathactor.h
index a21b4195..f4574355 100644
--- a/LEGO1/islepathactor.h
+++ b/LEGO1/islepathactor.h
@@ -6,7 +6,7 @@
 #include "mxtypes.h"
 
 // VTABLE 0x100d4398
-// SIZE >= 0x230
+// SIZE 0x160
 class IslePathActor : public LegoPathActor
 {
 public: 
diff --git a/LEGO1/legoactor.cpp b/LEGO1/legoactor.cpp
new file mode 100644
index 00000000..c26cc1fc
--- /dev/null
+++ b/LEGO1/legoactor.cpp
@@ -0,0 +1,3 @@
+#include "legoactor.h"
+
+DECOMP_SIZE_ASSERT(LegoActor, 0x78)
diff --git a/LEGO1/legoactor.h b/LEGO1/legoactor.h
index 9b23e943..b35df90b 100644
--- a/LEGO1/legoactor.h
+++ b/LEGO1/legoactor.h
@@ -20,6 +20,10 @@ class LegoActor : public LegoEntity
   {
     return !strcmp(name, LegoActor::ClassName()) || LegoEntity::IsA(name);
   }
+
+private:
+  undefined unk68[0x10];
+
 };
 
 #endif // LEGOACTOR_H
diff --git a/LEGO1/legoentity.cpp b/LEGO1/legoentity.cpp
index b79bc587..b8ed69f9 100644
--- a/LEGO1/legoentity.cpp
+++ b/LEGO1/legoentity.cpp
@@ -1,5 +1,7 @@
 #include "legoentity.h"
 
+DECOMP_SIZE_ASSERT(LegoEntity, 0x68)
+
 // OFFSET: LEGO1 0x1000c290
 LegoEntity::~LegoEntity()
 {
diff --git a/LEGO1/legoentity.h b/LEGO1/legoentity.h
index 46aea940..fdfe997f 100644
--- a/LEGO1/legoentity.h
+++ b/LEGO1/legoentity.h
@@ -4,6 +4,7 @@
 #include "mxentity.h"
 
 // VTABLE 0x100d4858
+// SIZE 0x68 (probably)
 class LegoEntity : public MxEntity
 {
 public:
diff --git a/LEGO1/legopathactor.cpp b/LEGO1/legopathactor.cpp
index 336cdc13..f1c39b82 100644
--- a/LEGO1/legopathactor.cpp
+++ b/LEGO1/legopathactor.cpp
@@ -1,5 +1,7 @@
 #include "legopathactor.h"
 
+DECOMP_SIZE_ASSERT(LegoPathActor, 0x154)
+
 // OFFSET: LEGO1 0x1002d700 STUB
 LegoPathActor::LegoPathActor()
 {
diff --git a/LEGO1/legopathactor.h b/LEGO1/legopathactor.h
index 7a2b1402..7e524b08 100644
--- a/LEGO1/legopathactor.h
+++ b/LEGO1/legopathactor.h
@@ -27,7 +27,9 @@ class LegoPathActor : public LegoActor
   }
 
   // TODO: the types. Pizza needs this as public:
+  undefined unk78[0xc4];
   MxS32 m_unk13c;
+  undefined unk140[0x14];
 };
 
 #endif // LEGOPATHACTOR_H
diff --git a/LEGO1/mxentity.cpp b/LEGO1/mxentity.cpp
index 1b5ea84f..da536504 100644
--- a/LEGO1/mxentity.cpp
+++ b/LEGO1/mxentity.cpp
@@ -1,5 +1,7 @@
 #include "mxentity.h"
 
+DECOMP_SIZE_ASSERT(MxEntity, 0x68)
+
 // OFFSET: LEGO1 0x1001d190
 MxEntity::MxEntity()
 {
@@ -9,4 +11,4 @@ MxEntity::MxEntity()
 // OFFSET: LEGO1 0x1000c110
 MxEntity::~MxEntity()
 {
-}
\ No newline at end of file
+}
diff --git a/LEGO1/mxentity.h b/LEGO1/mxentity.h
index a7e26e37..dc959c35 100644
--- a/LEGO1/mxentity.h
+++ b/LEGO1/mxentity.h
@@ -1,11 +1,13 @@
 #ifndef MXENTITY_H
 #define MXENTITY_H
 
+#include "decomp.h"
 #include "mxatomid.h"
 #include "mxcore.h"
 #include "mxtypes.h"
 
 // VTABLE 0x100d5390
+// SIZE 0x68 or less
 class MxEntity : public MxCore
 {
 public:
@@ -27,6 +29,7 @@ class MxEntity : public MxCore
 private:
   MxS32 m_mxEntityId; // 0x8
   MxAtomId m_atom; // 0xc
+  undefined m_unk10[0x58];
 };
 
 #endif // MXENTITY_H