If you know about when and where the dog is going to drop the disc, then start to predict and cue the drop at that time.
When the dog is retrieving the disc and gets about to the Spot is a “go to a place”, or “go to a mat” behavior. This means that the dog seeks out and performs a duration behavior on a spot of the where she’s going to drop, give the cue. Predict the likely drop spot and cue it.
This should result in very fast compliance with the cue. The time between the cue and the performance of the behavior should be very small if your prediction was correct.
Be careful not to cue too early. Cuing too early or making bad predictions can create and reinforce latency on the drop cue.
Predicting and cuing the drop creates a situation where “teeth off” is essentially paired with the cue and is reinforced with something awesome. Teaching the drop with low latency can be a challenge, but predicting and cuing as a drop tactic can quickly reduce latency.