I'm assuming you're using Isospeed Baseline poly. If it is, I'm not surprised about the notching as it is a very soft poly.
Another reason could be that you are actually hitting much harder at ELT due to the low power. You may not be feeling it due to the extra comfort and plushness though. That is just my experience with ELT poly.
I prefer syn gut as it offers greater comfort, pocketing and better feel. Poly still has a certain harshness to it at low tensions that I did not like. Power wise, I think SG is much better than ELT poly. Somehow, I am also able to generate more spin with SG than poly.