The Alfa controller antennas have nothing to do with which version of the GPS you have. My advice on the cardboard mod is if you get good consistent GPS lock, don't change anything. The V2 shield from 3DR is supposed to be good, but I don't have one. I did the cardboard mod (with 3D printed spacers) on all my Rev A Solos, but honestly never had any real issues.
That being said the cardboard mod is very easy, and free so why not?