(IF) you decide to go with something like this, use the largest diameter pipe you can, minimum 8" round (preferrably 10-12") and make sure you have some pitch to it on the way out. Going vertical is best if you can live with a hole in your roof.
In terms of application for your trailer, get a large 45 degree angled register boot, come off the stack with it and pipe it out the rear of your trailer. Large pipe and pitch is everything since you're restricting the draft somewhat by coming off the top with a 45. If you need more info let me know.