Very interesting your experience with the Alfa antennas. I had similar positive out comes from them as well. On stock around my neighborhood I could only reach 900 ft in one direction and got roughly 1,800 feet in another direction over the rail road tracks. Dji reflectors didn't help at all over the 900 ft direction but helped with the rail road track test direction. At work I was able to hit 1,900 feet on direction and two days ago I pulled 2,400 feet in another direction with stock and just the reflectors attached. I received my Alfa pair from amazon yesterday and just tested them 30 minutes ago at work. I was able to hit past the 2,000 mark where rth would start with still 3 bars on the screen where before it would be 1,900 feet with spotty one bar. The direction that I hit 2,400 feet with stock and reflectors I only had one spotty bar and barely could control the drone but today with the Alfa swap I went past to the 3,000 mark with still 2 bar solid and a nice video connection. I turned around because I couldn't see the drone and I was getting a little nervous.
Overall I think these Alfa antennas are the way to go if your looking for a solid connection 1,000 to 2,700 feet away. Anything thing past that is just teasing your luck and what not.