Thought I would pop up my mod experience FWIW...
Just spent 2 hours replacing std GPS 2mm thick PV2+ ver3 antenna with the 4mm bought from Mouser for $ 4.xx
Before I could not get a gps lock at home due to all the trees, even in largest clearing (approx. 50x50ft); typically 4-5 sats, sometimes would pop to 6 for about 30 sec. I used to wait for the 6 sat and take off up to 50 or so feet to go over the barn for more sky showing, then it would increase from there and I could fly up to 175ft to clear the forest.
After mod, I sit at 6-7 sats in same clearing.I have not yet flown as I wore all batts down during my testing on times.
Interesting that the 4mm is slightly different length and width, so it does not fit into the exact place as the OEM one; I cocked it 45 degrees and was able to then mount it without cutting any plastic. Testing this 45 twist in upper floor office, I could get 3-4 sats (inside) with the gps board just sitting on insulating pc of paper over an ESC arm.... I did not think it would matter, but to be sure, I went ahead and put it in same orientation as close as possible (so not cocked 45 degrees) and retested same way: exact same results - 3-4 sats. So that confirmed for me that you can **** it to make it fit and it will have no negative effect. I left it straight since I went ahead and pulled the glue strip cover. I did have to use dikes and cut one pc of frameing to let thinker antenna fit. It did not go all the way down in old mount either - it prob is up that 2mm extra, but if you are just careful and tighten all 4 mounting screws slowly to just free to just touching and don't go much farther, you will not crack the pcb and it will be ok fit.
Back together, with the shields in place, the same location that gave 3-4 open showed 5-6; so their shielding is effective.
Outside on ground and 6-7 where before it was 5-6.
I am happy with this change. Hope this encourages others to add the extra 1.5db gain.