I hate to sound like a grinch, but DIY sattelite radio antennas are a bad idea.
Those antennas suck, plain and simple, the companys who make them (dei, terk, delphi, etc) either, dont know how to make a good antenna, or need to make them how they are.
Problem with the antenna wires is that over time, the flexing and crushing, and bending that is applied to the antenna wire over time from running it though any door / window/ sunroof gasket or such, will lead you to the all too well known ANTENNA NOT DETECTED error on your sat radio.
My suggestion, pay the 25 bucks it costs to get your $40-$50 antenna run by a car audio place, cause if how they did it ends up causing that problem, they will have to replace it.
My $.02