I just came across this thread.
One point I discovered when configuring an F9P for RTK - the latest firmware for uBlox F9P (1.32 as I recall) will not handle a rate over 7hz with more than 2 constellations. You can find information about this in the uBlox Support Portal.
That meant I had to limit constellations to two(I chose GPS and GLOSS), and set the refresh rate to 10hz. (100ms)