I was too scared to go over 600whp on pump gas because detonation. I went 10:1 compression for response, but I'm guessing if you go 9.5:1 the difference would be negligible and you could boost a bit more.
This is my final E85 21psi tune with ID1000s at 90%+ IDC with CJM Stage 3 RFS (Twin 255 pumps):
I'm probably going to switch out to ID1300s sometime soon.