I finally got around to replacing the stock ceramic GPS antenna with the 4mm upgraded one. I haven't done any testing in the past other than to notice when I flew via the iPad Ground Station app. With the stock GPS setup I don't recall ever seeing more than 8 satellites and usually it's about 7 when my P2 is sitting on the ground. A quick test from my driveway got a GPS lock in about 20-25 seconds and with 12 satellites. Using an iPhone app to check GPS satellite coverage with an elevation mask of 0 degrees the MAX satellites possible would have been 14. I got 12 out of 14 just sitting on the ground in my driveway. with lots of trees and houses around. I flew up to about 100 feet and watched on the GS app but it never got about 12. I landed the P2 and turned off the props. I put my hand over the top of the phantom and the satellite count dropped to 6. I took my hand away it quickly climbed back to 12! The upgrade was pretty easy. I had two different types of solder wick braided material and that was the hardest part trying to get the solder out of the hole to put the new antenna on. Very pleased with the outcome of this. If you have any specific questions, please ask and I'll do my best to help.