Before you go fretting (and drilling holes) about where to place the Sirius magnetic antenna, check out several locations WITHIN your RV.
When Sirius says that the antenna needs a clear view of the sky, they mean at RADIO FREQUENCIES, not visible light frequencies.
The Sirius Sat Radio signal is in the 2.3 GHz range. Most computer Wi-Fi routers are in the 2.4 GHz range. That means that with NO METAL overhead obstruction, your Sat antenna will work wherever your computer or Wi-Fi will work.
For years, my Sirius Sat antenna lived under the mattress in the cab-over bed area. Now it sits in the dash just behind the windshield wipers.
Tim