AboveTheClouds

I forgot some precisions (don't know how to edit my post...). I made this range test using a Spark and an iPad pro. Both the RC and the Spark have the lastest FW versions and I used DJI Go 4 version 4.1.5. I tried the .DJI.configs method before but it didn't work for me... Hope this helps!

The Marcocappe technique works perfectly fine for me! I have an android and an IOS device and I used a different version of the modded app (v25) but the result is the same: I just have to hit cancel when DJI Go 4 (on IOS) asks me if I want to change country settings and voila! I went to more than 2km with just minor video interruptions before deciding to going back home (far enough to prove without a doubt that I'm in FCC mode, before my max flight distance was approx. 500m). I switched to 2.4GHz and used an OTG cable but I'm not sure the OTG helped me much. I don't want to fly that far every day but that assures me a solid connection. Thanks a lot Marcocappe!