GPS underneath carbon laminate

In my preparations for Roll Over America (Yes, I decided to take the plunge and do the Coast-to-Coast ride of 4500km in 4 weeks with some 40 other velomobiles) I was wondering how much worse the GPS reception of my Garmin 60CX would be under the carbon top of my Mango Sport. Carbon has a reputation of blocking radio signals and conducting electricity. My Garmin usually sits on top of the wheelarch well underneath the top of the Mango, so in the worst case I shouldn't have any GPS reception at all. Fortunately it seemed to be not that bad at all, since I have navigated with the Garmin and my iPhone while riding without dramatic loss of GPS reception. It does get worse though, as I can see when I move the Garmin under the "hood". To give an idea how much the reception worsens, I made two photos:

 The first photo is made with the Garmin looking at the clear sky. It was cloudy and I was parked right next to houses. Not the best circumstances, but the chipset of the Garmin has no problem with it.





The photo below shows the GPS reception with the Garmin under the carbon hood.  The reception is noticably less, but still good enough to navigate accurately. There is no need for a seperate antenna that pops out of the body, so I don't have to make yet another hole ;-)