Idle Shake/Jagged RPM Log

I am tuning on a 2001 Z06. Fresh rebuilt motor, all stock LS6 except a CompCams XR277HR (224/228 0.535/0.537).

I have gotten the idle/no load VE table close. (Needs more work, though, but it's enough that with close loop enabled, things are 1.00 Lambda).
I have gotten the idle robust, in that it does not surge/stall. I can drive off from a stop only by lifting off the clutch and it will motor along at 900rpm in 1st without bucking.

However the idle has a shake that will rock the whole car and the RPM plot is jagged +/-75rpm of set point.
Idle is set to 850rpm. I have also tried 875 and it doesn't correct things. This already sounds kind of high for this cam?
Tried playing with base idle timing. Tried holding it steady with VCM at a variety of settings from 16-28deg. All behave roughly the same.
I have been trying to mellow out the under/overspeed timing thinking the adaptive spark might be chasing the cam-lope too aggressively. Not helping. Even with spark held at a fixed value it shakes around.
RAF is not perfect at lower temps, but it's pretty damn close at 180F+
Good amount of vacuum (50-52kpa MAP)

Does this look like a "normal" amount of lope/chop for this small of a cam? Am I wasting my time chasing that which cannot be corrected?

Thanks for any suggestions.

I have attached a log+config & tune. (Tune is slightly modded since time of log...Was 850idle with 20 deg spark during the log).
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