I use a constant 850MHz with SR enabled and it's very stable.
Only problem is that after a while minimum frequency resets to 125 which makes the phone a bit sluggish.
Haven't pinpointed the culprit yet.
I use ondemand governor so it's not the bug from the conservative governor which resets to 125 when hanging up.
And 125 is excluded from my frequencies list.

This are the settings I use for my custom clocks:

MINFREQ=850
MAXFREQ=850
FREQS="0:25,90 850:48,430"
SMARTREFLEX_VDD1=1
SMARTREFLEX_VDD2=1
GOVERNOR=ondemand
IGNORE_NICE_LOAD=1
UP_THRESHOLD=75
SAMPLING_RATE=150000
POWERSAVE_BIAS=0