IMO it's the amount of time in between the dash and the C-Stick down. I was actually practicing some Bombslide to DAC stuff the other day, and I noticed that the sooner I pressed down the C-Stick, the farther I went. I think it's an issue with the speed of your dash when you press C-Stick down. Obviously, your Dash speed has the biggest increase at the beggining. (0 Speed to initial dash speed) Therefore, when you decrease Link's friction by DACing, you have all the momentum pushing Link. Obviously, things get slower as you progress through Link's frames. (initial dash speed to slightly faster slight speed) When you're too late, there isn't enough change in momentum to push Link forward. That's the secret to Link's DAC. (I think)