My experience is that the satellite radio antennae come prewired and splicing is no advised. I used a magnetic-base vehicle antenna on mine. I have a roof vent location close to where our entertainment center is, and the vent has a Maxx-Air cover on it.
I got a large fender washer and attached it to the top of the Maxx-Air cover with hot glue. This was the highest point on the trailer, and the magnet mount antenna holds nicely on the big washer. Then route the wire around the vent, and you can get past the inside flange to get the wire in the ceiling and then take it to where you need it. I brought mine down the wall of the entertainment center and left about 6" of wire on the counter top to connect the receiver when I need to. Note there is NO need to disturb any of the sealing around the vent and the roof.