I believe the maximum height in the U.S. is now as it is here 400FT. I've tested my Spark to link loss over water here and find (using OTG) it gets flakey at around 700M, I'm on the CE power output which is less than the U.S. models. Being WiFi not occusync it's VERY particular about antenna orientation. Directly above at 2000FT would be worse than 2000FT away out at 45º angle at 400FT height with the antenna correctly oriented.
Before anyone starts, I only qualified as a Telecommunications technician almost 40 years ago, hold an Advanced Class Amateur Radio Certificate, Maritime Operators Certificate and an Aeronautical Radio Operators Certificate along with the Remote Pilot's certification so no, I guess I wouldn't know anything.
I'm not going directly into the "fly aways" issue, I've not had one but of course I could. There are several videos on YouTube on how to avoid that, I'd just suggest any spark owner new or old watch them.
I just thought I'd add to my earlier post above to say that I saw three new Sparks in the box today with manufacturing stickers marked December 2018 so production is not ramping down and my dealer tells me there are large stocks in inventory so that suggests we are not going to see a new model before mid year. Most of the upgrades people would want like a 3 axis gimbal, 4k and Occusynch would put the price point where it would canabilise sales from teh Mavic Air so we may not see much of an upgrade at all.
Regards
Ari