I am getting the rightmost category column stretched way more than the other category columns. 
Here is my xml -  
  <?xml version="1.0" encoding="utf-8" ?>  
- <chart xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" dateFormat="mm/dd/yyyy" caption="Phase 1 Trials Gantt Chart" subCaption="From 2009 to 2013" ganttWidthPercent="75" ganttPaneDuration="1" ganttPaneDurationUnit="y"> 
- <categories> 
  <category start="01/01/2009" end="12/31/2009" label="2009" />  
  <category start="01/01/2010" end="12/31/2010" label="2010" />  
  <category start="01/01/2011" end="12/31/2011" label="2011" />  
  <category start="01/01/2012" end="12/31/2012" label="2012" />  
  <category start="01/01/2013" end="12/31/2013" label="2013" />  
  </categories> 
- <categories> 
  <category start="01/01/2009" end="03/31/2009" label="Qtr 1" />  
  <category start="04/01/2009" end="06/30/2009" label="Qtr 2" />  
  <category start="07/01/2009" end="09/30/2009" label="Qtr 3" />  
  <category start="10/01/2009" end="12/31/2009" label="Qtr 4" />  
  <category start="01/01/2010" end="03/31/2010" label="Qtr 1" />  
  <category start="04/01/2010" end="06/30/2010" label="Qtr 2" />  
  <category start="07/01/2010" end="09/30/2010" label="Qtr 3" />  
  <category start="10/01/2010" end="12/31/2010" label="Qtr 4" />  
  <category start="01/01/2011" end="03/31/2011" label="Qtr 1" />  
  <category start="04/01/2011" end="06/30/2011" label="Qtr 2" />  
  <category start="07/01/2011" end="09/30/2011" label="Qtr 3" />  
  <category start="10/01/2011" end="12/31/2011" label="Qtr 4" />  
  <category start="01/01/2012" end="03/31/2012" label="Qtr 1" />  
  <category start="04/01/2012" end="06/30/2012" label="Qtr 2" />  
  <category start="07/01/2012" end="09/30/2012" label="Qtr 3" />  
  <category start="10/01/2012" end="12/31/2012" label="Qtr 4" />  
  <category start="01/01/2013" end="03/31/2013" label="Qtr 1" />  
  <category start="04/01/2013" end="06/30/2013" label="Qtr 2" />  
  <category start="07/01/2013" end="09/30/2013" label="Qtr 3" />  
  <category start="10/01/2013" end="12/31/2013" label="Qtr 4" />  
  </categories> 
- <processes positionInGrid="left" headerText="Trial Name" headerIsBold="1" align="left" headerAlign="left"> 
  <process id="0" label="DI-OC, OCP, HRT" />  
  <process id="1" label="AAAA-Image drug in uterus" /> 
<process id="2" label="DI-OC, OCP, HRT" />  
  <process id="3" label="AAAA-Image drug in uterus" /> 
  <process id="4" label="AAAA-Image drug in uterus" />  
  <process id="5" label="AAAA-Image drug in uterus" /> 
  <process id="6" label="AAAA-Image drug in uterus" /> 
  <process id="7" label="AAAA-Image drug in uterus" /> 
  <process id="8" label="AAAA-Image drug in uterus" />  
  <process id="9" label="AAAA-Image drug in uterus" /> 
  <process id="10" label="AAAA-Image drug in uterus" />  
  <process id="11" label="AAAA-Image drug in uterus" /> 
<process id="12" label="DI-OC, OCP, HRT" />  
  <process id="13" label="AAAA-Image drug in uterus" /> 
  </processes> 
- <tasks> 
  <task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="0" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="1" processId="1" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="2" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="2" processId="3" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="4" height="15%" topPadding="25%" />  
  <task start="10/17/2006" end="12/30/2008" id="3" processId="5" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="6" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="4" processId="7" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="8" height="15%" topPadding="25%" />  
  <task start="10/17/2006" end="12/30/2008" id="5" processId="1" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="9" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="6" processId="10" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="11" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="7" processId="12" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="13" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="8" processId="14" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="15" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="9" processId="16" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="17" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="10" processId="18" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="0" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="11" processId="1" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="0" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="12" processId="1" height="15%" topPadding="25%" /> 
<task start="10/17/2006 8:00:00 AM" end="12/28/2007 5:00:00 PM" id="0" processId="0" height="15%" topPadding="25%" />  
  <task start="10/17/2006 8:00:00 AM" end="12/30/2008 5:00:00 PM" id="13" processId="1" height="15%" topPadding="25%" />  
  </tasks> 
  </chart>