I think people are mis-understanding the shot. Look at the original shot, the hole and the section of hull being removed are the same size (you can compare the lines on the surface of the saucer). The saucer and removable section were shot in one take, it's not possible for that removable piece to be bigger than the hole because it was literally taken from it.
Agreed. The final energy beam may not be as wide as it should be, but the hole itself appears to be the same size as in the SD shot.