Visual representation of frame trapping (arrows)

This is only theory. I don't have any real footage on how frame trapping. If anyone have better experience over it, please tell me if it works.

 Arrows can be effective to frame trap as they have a very low cooldown when tossed from the air (only 19 frames) while covering a very large area.

Here is the scenario : Pit Downthrow, read the airdodge and punish with Dair which pops the Marth up (airjump used : 1) : https://youtu.be/CDGmz8nme6s?t=30s
We will frame trap the option : Fast fall toward the stage to recover from below.