I had the same problem with the Biscuit that I modified like that. Others have raved about the results when cutting away the bristles so that the vanes clear better, but it was a problem for me as it was for you. I do not shoot with a string loop, and some of the guys who modify the Biscuit by trimming areas completely apparently do shoot a loop.

I personally have had much better luck by trimming the back of the Biscuit (towards the string) flat. No arrow dropping and good accuracy with minimal vane distortion.

I am using an aluminum Biscuit and shooting ICS carbons and ACC arrows.