It'll do 6 slabs. Double up on each hanger, add only 10 minutes. 12.5 pounds of charcoal.
I got me one of these Orion's last summer (for $35 off Craigs List), it is now my go to rib machine. Much quicker(under 2 hours), less work and better tasting product than I was spending about 7 hours on the smoker with. Only down fall to mention so far is all I can do is 3 racks of spares at a time; may have to get another one! I'm looking forward to trying this on other meals; but no matter the outcome; I will keep the Orion as my quick rib machine!
Another cooker I learned about that works off the same principle but is meant to work with your campfire is the CanCooker. http://www.cancooker.com/ I may have to get one of these for first hand comparison!