diff --git a/korman/properties/prop_world.py b/korman/properties/prop_world.py
index 453f2d9..5e223af 100644
--- a/korman/properties/prop_world.py
+++ b/korman/properties/prop_world.py
@@ -148,6 +148,14 @@ class PlasmaPage(bpy.types.PropertyGroup):
 
 class PlasmaAge(bpy.types.PropertyGroup):
     def export(self, exporter):
+        if exporter.mgr.getVer() == pvMoul:
+            log_func = exporter.report.warn
+        else:
+            log_func = exporter.report.port
+        if self.seq_prefix <= self.MOUL_PREFIX_RANGE[0] or self.seq_prefix >= self.MOUL_PREFIX_RANGE[1]:
+            log_func("Age Sequence Prefix {} is potentially out of range (should be between {} and {})",
+                     self.seq_prefix, *self.MOUL_PREFIX_RANGE)
+
         _age_info = plAgeInfo()
         _age_info.dayLength = self.day_length
         _age_info.lingerTime = 180 # this is fairly standard
@@ -157,6 +165,10 @@ class PlasmaAge(bpy.types.PropertyGroup):
         _age_info.startDateTime = self.start_time
         return _age_info
 
+    # Sequence prefix helpers
+    MOUL_PREFIX_RANGE = ((pow(2, 16) - pow(2, 15)) * -1, pow(2, 15) - 1)
+    SP_PRFIX_RANGE = ((pow(2, 24) - pow(2, 23)) * -1, pow(2, 23) - 1)
+
     day_length = FloatProperty(name="Day Length",
                                description="Length of a day (in hours) on this age",
                                default=30.230000,
@@ -169,7 +181,10 @@ class PlasmaAge(bpy.types.PropertyGroup):
                              min=0)
     seq_prefix = IntProperty(name="Sequence Prefix",
                              description="A unique numerical ID for this age",
+                             min=SP_PRFIX_RANGE[0],
                              soft_min=0,  # Negative indicates global--advanced users only
+                             soft_max=MOUL_PREFIX_RANGE[1],
+                             max=SP_PRFIX_RANGE[1],
                              default=100)
     pages = CollectionProperty(name="Pages",
                                description="Registry pages for this age",
diff --git a/korman/ui/ui_world.py b/korman/ui/ui_world.py
index c4bcb8c..3ed422e 100644
--- a/korman/ui/ui_world.py
+++ b/korman/ui/ui_world.py
@@ -210,6 +210,8 @@ class PlasmaAgePanel(AgeButtonsPanel, bpy.types.Panel):
 
         # Age Names should really be legal Python 2.x identifiers for AgeSDLHooks
         legal_identifier = korlib.is_legal_python2_identifier(age.age_name)
+        illegal_age_name = not legal_identifier or '_' in age.age_name
+        bad_prefix = age.seq_prefix >= age.MOUL_PREFIX_RANGE[1] or age.seq_prefix <= age.MOUL_PREFIX_RANGE[0]
 
         # Core settings
         layout.separator()
@@ -222,17 +224,28 @@ class PlasmaAgePanel(AgeButtonsPanel, bpy.types.Panel):
 
         col = split.column()
         col.label("Age Settings:")
+        col.alert = bad_prefix
         col.prop(age, "seq_prefix", text="ID")
-        col.alert = not legal_identifier or '_' in age.age_name
+        col.alert = illegal_age_name
         col.prop(age, "age_name", text="")
 
+        if age.seq_prefix >= age.MOUL_PREFIX_RANGE[1]:
+            layout.label(text="Your sequence prefix is too high for Myst Online: Uru Live", icon="ERROR")
+        elif age.seq_prefix <= age.MOUL_PREFIX_RANGE[0]:
+            # Unlikely.
+            layout.label(text="Your sequence prefix is too low for Myst Online: Uru Live", icon="ERROR")
+
         # Display a hint if the identifier is illegal
-        if not legal_identifier:
-            if korlib.is_python_keyword(age.age_name):
+        if illegal_age_name:
+            if not age.age_name:
+                layout.label(text="Age names cannot be empty", icon="ERROR")
+            elif korlib.is_python_keyword(age.age_name):
                 layout.label(text="Ages should not be named the same as a Python keyword", icon="ERROR")
             elif age.age_sdl:
                 fixed_identifier = korlib.replace_python2_identifier(age.age_name)
                 layout.label(text="Age's SDL will use the name '{}'".format(fixed_identifier), icon="ERROR")
+            if '_' in age.age_name:
+                layout.label(text="Age names should not contain underscores", icon="ERROR")
 
         layout.separator()
         split = layout.split()