RE: Berg Micro RX + GWS Xtal -- Not a Marriage.
I have had many discussions with Castle Creations about crystals. I have probably sold as many Berg receivers as anybody, over 1200 to date and I have sold two Berg crystals because the people that bought the receivers were told by Castle they must use Berg crystals. Guys wake up. This is like Ford or Chevrolet telling you that you must you Fomoco oil or Delco oil or whatever it is that Chevrolet sells. Berg wants to sell you crystals.
I have used GWS crystals in dozens of my personal airplanes and they work fine. I personally prefer Performance Device crystals but they are having some issues with the two distributors and you just don't see them as readily available in the local hobby shops but they are the best crystal IMHO. Use whatever you can get, all of the UM-1 crystals will work.