I just gone mine done last week this is link about it.http://www.smokingmeatforums.com/viewtopic.php?t=2016
My stacks I used 4" stove stacks and just drilled a hole and put in a 4" dampaner. They are 24" tall incase you are wondering also.
The pulled pork I just pulled off of it tonight I have to say it made it well worth it.
It if a fun build mine took about a weekend of work. I was able to buy my barrels from a local company in Chicago and I got them pulled off the line before they went to paint so I had 3 fresh new barrels in bear metal.
If you have any questions please do ask I will be very willing to help.