I'm fairly new to this PID stuff but I'd guess on a 525 frame the standard/default settings will be very close
We have 2 KK X525's up and running and good initial PIDs are:
(Use the PIDs menu in the config section of the Mission Planner)
stab ang rate P = .1
stab cont P = 4.5
yaw ang P = .15
yaw stab P = 7 good start for stabilize
Alt err P = .5
Thrust rate P = .2 good for alt hold
Loiter ang rate P = 2.5
Loiter speed P = .47 good start for loiter but too wide a loiter radius 10 - 15 feet.
I'm looking for any other values too, but these will get you started.
Will this work well for a Hobbyking 540mm frame with NTM 26-28A 1200kv motors ?