diff --git a/core/src/net/sf/openrocket/aerodynamics/BarrowmanCalculator.java b/core/src/net/sf/openrocket/aerodynamics/BarrowmanCalculator.java
index 880db8151..e0c0aab8d 100644
--- a/core/src/net/sf/openrocket/aerodynamics/BarrowmanCalculator.java
+++ b/core/src/net/sf/openrocket/aerodynamics/BarrowmanCalculator.java
@@ -571,11 +571,9 @@ public class BarrowmanCalculator extends AbstractAerodynamicCalculator {
 	 * @return
 	 */
 	private double calculateBaseDrag(FlightConfiguration configuration, FlightConditions conditions,
-			Map<RocketComponent, AerodynamicForces> map, WarningSet warnings) {
+									 Map<RocketComponent, AerodynamicForces> map, WarningSet warnings) {
 		
 		double base, total;
-		double radius = 0;
-		RocketComponent prevComponent = null;
 		
 		if (calcMap == null)
 			buildCalcMap(configuration);
@@ -583,36 +581,51 @@ public class BarrowmanCalculator extends AbstractAerodynamicCalculator {
 		base = calculateBaseCD(conditions.getMach());
 		total = 0;
 		
-		for (RocketComponent c : configuration.getActiveComponents()) {
+		final InstanceMap imap = configuration.getActiveInstances();
+	    for(Map.Entry<RocketComponent, ArrayList<InstanceContext>> entry: imap.entrySet() ) {
+			final RocketComponent c = entry.getKey();
+			
 			if (!(c instanceof SymmetricComponent))
 				continue;
 			
 			SymmetricComponent s = (SymmetricComponent) c;
-
-			if(c.isCDOverridden()) {
-				total += c.getOverrideCD();
-				continue;
-			}
 			
-			if (radius > s.getForeRadius()) {
-				double area = Math.PI * (pow2(radius) - pow2(s.getForeRadius()));
-				double cd = base * area / conditions.getRefArea();
-				total += cd;
-				if (map != null) {
-					map.get(prevComponent).setBaseCD(cd);
+			// iterate across component instances
+			final ArrayList<InstanceContext> contextList = entry.getValue();
+			for(InstanceContext context: contextList ) {
+				if(c.isCDOverridden()) {
+					total += c.getOverrideCD();
+					continue;
+				}
+				
+				// if aft radius of previous component is greater than my forward radius, set
+				// its aft CD
+				double radius = 0;
+				final SymmetricComponent prevComponent = s.getPreviousSymmetricComponent();
+				if (prevComponent != null) {
+					radius = prevComponent.getAftRadius();
+				}
+				
+				if (radius > s.getForeRadius()) {
+					double area = Math.PI * (pow2(radius) - pow2(s.getForeRadius()));
+					double cd = base * area / conditions.getRefArea();
+					total += cd;
+					if ((map != null) && (prevComponent != null)) {
+						map.get(prevComponent).setBaseCD(cd);
+					}
+				}
+				
+				// if I'm the last componenet, set my base CD
+				// note I can't depend on the iterator serving up components in order,
+				// so I can't just do this after the last iteration.
+				if (s.getNextSymmetricComponent() == null) {
+					double area = Math.PI * pow2(s.getAftRadius());
+					double cd = base * area / conditions.getRefArea();
+					total += cd;
+					if (map != null) {
+						map.get(s).setBaseCD(cd);
+					}
 				}
-			}
-			
-			radius = s.getAftRadius();
-			prevComponent = c;
-		}
-		
-		if (radius > 0) {
-			double area = Math.PI * pow2(radius);
-			double cd = base * area / conditions.getRefArea();
-			total += cd;
-			if (map != null) {
-				map.get(prevComponent).setBaseCD(cd);
 			}
 		}
 		
diff --git a/core/src/net/sf/openrocket/rocketcomponent/SymmetricComponent.java b/core/src/net/sf/openrocket/rocketcomponent/SymmetricComponent.java
index 35957c459..64958596e 100644
--- a/core/src/net/sf/openrocket/rocketcomponent/SymmetricComponent.java
+++ b/core/src/net/sf/openrocket/rocketcomponent/SymmetricComponent.java
@@ -7,6 +7,7 @@ import java.util.Collection;
 import java.util.List;
 
 import net.sf.openrocket.preset.ComponentPreset;
+import net.sf.openrocket.rocketcomponent.PodSet;
 import net.sf.openrocket.rocketcomponent.position.AxialMethod;
 import net.sf.openrocket.util.Coordinate;
 import net.sf.openrocket.util.MathUtil;
@@ -561,34 +562,37 @@ public abstract class SymmetricComponent extends BodyComponent implements Radial
 
 	/**
 	 * Return the previous symmetric component, or null if none exists.
-	 * NOTE: This method currently assumes that there are no external
-	 * "pods".
 	 * 
 	 * @return	the previous SymmetricComponent, or null.
 	 */
 	public final SymmetricComponent getPreviousSymmetricComponent() {
 		RocketComponent c;
 		for (c = this.getPreviousComponent(); c != null; c = c.getPreviousComponent()) {
+			if (c instanceof PodSet) {
+				return null;
+			}
 			if (c instanceof SymmetricComponent) {
 				return (SymmetricComponent) c;
 			}
 			if (!(c instanceof AxialStage) &&
-					(c.axialMethod == AxialMethod.AFTER))
+				(c.axialMethod == AxialMethod.AFTER)) {
 				return null; // Bad component type as "parent"
+			}
 		}
 		return null;
 	}
 	
 	/**
 	 * Return the next symmetric component, or null if none exists.
-	 * NOTE: This method currently assumes that there are no external
-	 * "pods".
 	 * 
 	 * @return	the next SymmetricComponent, or null.
 	 */
-	protected final SymmetricComponent getNextSymmetricComponent() {
+	public final SymmetricComponent getNextSymmetricComponent() {
 		RocketComponent c;
 		for (c = this.getNextComponent(); c != null; c = c.getNextComponent()) {
+			if (c instanceof PodSet) {
+				return null;
+			}
 			if (c instanceof SymmetricComponent) {
 				return (SymmetricComponent) c;
 			}