The size of the docked subs is taken into account when generating the level

Subsurface/Source/Map/Levels/Level.cs

@@ -183,8 +183,12 @@ namespace Barotrauma
             float avgValue = (backgroundColor.R + backgroundColor.G + backgroundColor.G) / 3;
             GameMain.LightManager.AmbientLight = new Color(backgroundColor * (10.0f / avgValue), 1.0f);
 
-            float minWidth = Submarine.MainSub == null ? 0.0f : Math.Max(Submarine.MainSub.Borders.Width, Submarine.MainSub.Borders.Height);
-            minWidth = Math.Max(minWidth, 6500.0f);
+            float minWidth = 6500.0f;
+            if (Submarine.MainSub != null)
+            {
+                Rectangle dockedSubBorders = Submarine.MainSub.GetDockedBorders();
+                minWidth = Math.Max(minWidth, Math.Max(dockedSubBorders.Width, dockedSubBorders.Height));
+            }
 
             startPosition = new Vector2(
                 Rand.Range(minWidth, minWidth * 2, false),

Subsurface/Source/Map/Submarine.cs

@@ -288,6 +288,30 @@ namespace Barotrauma
             tags &= ~tag;
         }
 
+        /// <summary>
+        /// Returns a rect that contains the borders of this sub and all subs docked to it
+        /// </summary>
+        public Rectangle GetDockedBorders()
+        {
+            Rectangle dockedBorders = Borders;
+            dockedBorders.Y -= dockedBorders.Height;
+
+            foreach (Submarine dockedSub in DockedTo)
+            {
+                Vector2 diff = dockedSub.Submarine == this ? dockedSub.WorldPosition : dockedSub.WorldPosition - WorldPosition;
+                    
+
+                Rectangle dockedSubBorders = dockedSub.Borders;
+                dockedSubBorders.Y -= dockedSubBorders.Height;
+                dockedSubBorders.Location += diff.ToPoint();
+
+                dockedBorders = Rectangle.Union(dockedBorders, dockedSubBorders);
+            }
+
+            dockedBorders.Y += dockedBorders.Height;
+            return dockedBorders;
+        }
+        
         //drawing ----------------------------------------------------
 
         public static void CullEntities(Camera cam)