When I first tried Trap, a gentleman shared the following with me, not sure if it will help or not, but here goes;
Gun hold as well as "eye hold" (where you look when calling for the target) is a very personal thing. Gun hold partially depends on whether you are a one-eyed or two-eyed shooter.
One-eyed shooters usually hold below the trap house roof to avoid the barrel's covering targets as they leave the house. Two eyed shooters, depending on how far over the house they hold, also consider the possibility of blocking their view of targets with the fore end and hand as they leave the house and hold to avoid that possibility. Blocking target's leaving the house is most likely on stations 2, 3, and 4 with 3 being the most likely.
Longer swings tend to be smoother swings. For that reason, high gun holds require more refined swings because they are shorter as well as better timing because targets must be intersected rather than overtaken. Short swings with a high hold also require better timing regarding exactly when to fire. On an "off" day, those who intersect using a high hold will have slightly more trouble because reaction times can vary as can the coordination required for short, smooth swings.
The advantage of a higher hold as was noted above, is that swings are shorter since the gun is already pointing nearer the height of targets when they are shot. There is less chance of a swing error since the gun is not moving as far. The challenge, along with needing to intersect targets, is that with a shorter swing, smooth swings can be more difficult to obtain. "Jerky" swings are on the opposite end of the scale and of course, are to be avoided.
Eye holds, regardless of the height of gun holds, are at the height where targets can first be seen clearly. It does little good to try to focus on blurred targets. The time it takes for the eyes to focus on targets is a contributing factor. For that reason, the height of an eye hold that works well for one shooter may not work for another. It takes time and experimentation to find just the right places; this is true regarding both the hight and horizontal aspects of the hold.
Practice is necessary when changing either eye or gun holds. How much time it takes to get used to a new one varies from shooter to shooter. It may take a only a squad or two or it may take a half-dozen. This is true for any change of gun or eye hold and for both one and two-eyed shooters.