You did not place the stretch selection windows appropriately and you did not adjust the angle offsets or the distance multipliers appropriately. The stretch windows should each surround one of the two corners, not both (that's why you need two stretch actions).
The angle offset should be obvious. 2° for one of them and -2° for the other.
The distance multipliers are less intuitive. Basically the distance multiplier defines the distance stretched per each unit that the grip is stretched. Because the stretch is at an angle, the distance the corner needs to move for the horizontal line to match the parameter to grip movement is greater than 1. I like to find the value by drawing a simple right triangle and then measuring the hypotenuse. In this case the grip movement is vertical and so the vertical line of the right triangle would be 1 to match 1 unit of movement of the grip. draw a horizontal line from the top of the 1 unit vertical line you drew. Next, from the starting point draw a line at the 88° angle. Where that 88° line and the horizontal line intersect finishes defining the right triangle. The length of the hypotenuse (88° line) is the necessary distance multiplier value.
Let me know if you need me to explain any of that more thoroughly.
