Hi Littlejack,
My thoughts is that whether plenty of coralline algea or not, it doesn't make me any more comforted if there is too much dosing causing a kh shock. The overshoot of kh is unlikely to be mitigated by the coralline algea consumption to prevent an ill effect on the SPS cause by the high kh level. Btw, one of the visible effect of KH overdose is the burn tip symptom.
Also, I would say that a rising kh could be less damaging then a lowering of kh base on my experience.