small adjustments to new node and position classes
diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
index 8eb2cbd..60e733d 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/NodeWritable.java
@@ -30,7 +30,7 @@
     }
     
     public NodeWritable() {
-        this(21);
+        this(0);
     }
     
     public NodeWritable(int kmerSize) {
diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java
index 49f1b11..5f72906 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionListWritable.java
@@ -30,6 +30,7 @@
     
     public PositionListWritable(List<PositionWritable> posns) {
         this();
+        setSize(posns.size());  // reserve space for all elements
         for (PositionWritable p : posns) {
             append(p);
         }
@@ -48,12 +49,7 @@
     }
     
     public void append(PositionWritable pos) {
-        if(pos != null){
-            setSize((1 + valueCount) * PositionWritable.LENGTH);
-            System.arraycopy(pos.getByteArray(), pos.getStartOffset(), storage, offset + valueCount
-                    * PositionWritable.LENGTH, pos.getLength());
-            valueCount += 1;
-        }
+        append(pos.getUUID());
     }
     
     /*
diff --git a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java
index 74ef9d5..7cf9bfc 100644
--- a/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java
+++ b/genomix/genomix-data/src/main/java/edu/uci/ics/genomix/type/PositionWritable.java
@@ -14,8 +14,7 @@
     private static final long serialVersionUID = 1L;
     protected byte[] storage;
     protected int offset;
-    public static final int LENGTH = 5;
-    public static final int LONGBYTES = 8;
+    public static final int LENGTH = 8;
     
     public PositionWritable() {
         storage = new byte[LENGTH];