David from Butcher BBQ has the best setup for this that I have seen. He has his two FEC-100's mounted to the floor in the back of his 23' foot trailer. His trailer does not have a ramp door since his are mounted to the floor and are only removed for repairs, etc. He has cut two holes (one for each cooker) in the back doors and mounted an RV electrical hatch door that can be purchased at any RV store (see link below). The hatch is mounted at the exact height to run the horizontal smoke stack out of the hatch door to the outside and then an elbow with an additional smoke stack to vent the smoke up. Then, a vent cap so rain, etc will not get into the smoke stack. This back portion of his trailer is separated from the front portion with the thick plastic barriers that you would find in Butcher shops or freezers to keep the cold air from escaping into the other sections. This is used to keep any smoke that escapes from opening the doors from getting into the "work" area of his trailer. He then has a small fan mounted on the ceiling under the vent in the back portion that pulls that smoke up and out of the trailer when he opens the cooker doors, etc.
http://www.race-mart.com/Bargman-BAR-60-14-002.html
Hope this helps....
Stu
Hogs on the Sauce