P4 (not pro) 1.x firmwares have not any heigh limit parameters.It seems that the heigh limit was build in program code.So if your P4 still running 1.x firmware ,you cannot modify the heigh limit.
But the newest P4 firmware 2.0,there are some heigh limit parameters in the firmware, same as Mavic. Lots of Mavic user modify them Mavic and fly above 500m. It seems work in P4(I have not tried.).
It is interesting. Maybe some new guy joined DJI,and want to fly unlimited,so make this backdoor to help him/her fly >500m secretly?
But the newest P4 firmware 2.0,there are some heigh limit parameters in the firmware, same as Mavic. Lots of Mavic user modify them Mavic and fly above 500m. It seems work in P4(I have not tried.).
It is interesting. Maybe some new guy joined DJI,and want to fly unlimited,so make this backdoor to help him/her fly >500m secretly?