Ive got duals on my with LTs and no cats and love it. If I had a dropped truck with those flat bumpers (cant remember the name right now) then I would have turn downs. But being lifted and having the exhaust setup that I have, I chose 4" tips out the back.

 

Roll Pans

 

I got one ordered from Autozone...

 

And now it's here...

 

Here's mine. I didn't want them blowing directly on anything on the trailer (not sure it would hurt anything), so I brought them out at the corners.