I'm in the same boat. I just ordered the 7+ and I have the Pro 3. I called DJI and they first said not good-try 6S+. Then I chatted and they said fine to use. Then I told them to double check and they said it had not been tested. So I assumed it was probably ok but they had not tested it because it was new.
I also asked them about using the LG V930 10 inch tablet with cellular and GPS and they said it had not been approved but the ipad mini 2 was ok. So now I need to decide to accept the LG tablet or send it back and maybe get the Mini 2.
Or I guess I could just use the I phone 7 +. It would be interesting to see how many people have used the 6 or 7+ and if it was a goiod experience.