I realize this is a pretty old thread. Lots of folks find these posts helpful though, and I thought it would be good to share an XM antenna install I just made. I recently purchased an '04 4runner that has a spoiler over the back glass. I was able to remove the spoiler easily (open back door, remove two screws covered by plastic plugs, then slide the spoiler DOWN).
Once the spoiler was off (I say off, but it is still connected via a wire to the brake light), I extended the size of the opening so I could get an antenna in there. The spoiler is either fiberglass or some sort of plastic and it's very hard to cut. I ended up using a dremmel tool to cut it (those round flat cutting disks).
Now I was concerned about having an antenna rattle around inside the spoiler. Thought about blowing in some expanding foam, but backed off that idea. Then I realized that I could take some JB weld (the epoxy kind where you mix two ingrediants) and a couple of large washers (cost 20 cents apiece). With this, I glued the washers to the inside of the spoiler. The XM antenna magnets hold the antenna to the washers and there is no rattle of any kind.
Then I fished the xm antenna connector down the raceway for brake light wiring. Note" there is a gromment that exists for the brake wire where it enters the 4 runner. This grommet is covered by the spoiler, so compromising it's water tightness doesn't look to be much of an issue.
Once the cable was inside under the roof covering, it was easy to run it to the radio. Very clean and totally hidden. Hope this helps someone - the washers and jb weld are key.
