The problem with most trailers is all the splitters and connections between the 'sat in' outside connection and your receiver box. These portable sat antennas need to have a good, uninterrupted cable run to the box. Many people just string a new straight-through line. I have a Winegard Pathway X2 and have the same situation.
I think that sometimes you can use your original set up if you pull off the outside panel, find the line going to your TV, detach it from any splitters and connect directly to the line running to your Tailgater.