I have not done an experiment, but mine is located in dash behind my instrument cluster. I always have 5-7 sats at any given time. Considering you only need 3 to triangulate your position, I don't see any problem with this.
Same here I had put my GPS antenna on the front dash for a while, which at that time I was getting 7-8 satellites. I recently moved it from the dash to underneath behind the instrument cluster and I still get 6-8 satellites.
I actually turned on the RNS and watch the satellites as I moved it to different places and it really didn't lose any satellites.