I'm not sure I can adequately describe how I do what I do, so bear with me on this. I've been trough all kinds of sxit from coils, vs. loops, to running line jamming up trying to go through too many too small guides, you name it, it has most likely happened to me.
Somewhere, either in these hallowed pages or maybe on you tube, is a discussion on holding coils vs. loops. After watching the video on that, I converted to loops. Eventually, I adopted George Cook's KISS system for holding loops. Originally each loop was equal. As time went on I began to hold the first loop coming off the water as the longer of the two. The theory being, greater line speed at the beginning of the cast is more able to pull the longer loop off the water, and as the cast nears its end and is slowing down, it only needs to pull the shorter loop off the water. Preferably, still having enough energy to come tight to the reel. I hold these loops over my lower hand pinky. But I grip the line with both top and bottom hand. Top hand middle & ring finger, (I think) line draped tight over the reel to bottom hand which is gripping between index finger & rod butt. When do I let go? Beats the hell outa me. Maybe a few milliseconds after I feel a good load on the rod????
Hard stop, high, shoot for the tree tops, not my style. When the line drops to the water, the heaviest part, the back of the head, will come down first, forming a drag producing loop that must be delt with. By aiming the cast lower, (think line drive rather than fly ball) that problem is minimized. Wherever the stop, to increase shooting efficiency and minimize the shock effect when everything comes tight to the reel & snaps back, there must be a follow through.
A tight loop develops the line speed needed to throw line drive casts. And, contrary to popular belief, slow action rods are capable of throwing tight loops. Like everything else, the application of power, the stop, the release, it's all in the timing. I don't know how to break that down into milliseconds. Time on the water, practice, practice, practice.