Looks nice. I bought some of this Al tubing to make an extended cvd for a similar project:
http://cgi.ebay.com/2-x-ALUMINIUM-ROUND-TUBE-8mm-OD-x-500mm-LONG-2mm-W-/250530711785?
How does its thickness compare to the Al tube you used originally? Mine won't need to be quite as long as yours so I'm hoping this will work.
-Brian