I had a need to cut a less than 4 X 4 ft hole for adding a basement vent in the main bathroom . The plumber cut the hole for a Great drywall repair.
I mounted the replacement piece of drywall and used some drywall shims.
The Repair looked great until the mounting of the wooden horizontal soap dish opened the horizontal seam crack.
The drywall repair piece needed caulk to re-enforce the thin horizontal seam above the vanity. I drilled holes and filled them with caulk to stabilize the thin seam above. The repair piece seam was too thin to take in enough mud on the horizontal top seam. Holes and caulk plugs stabilized the thin seam. Horizontal seams need to be wide enough to take in material on heavy use seams.
Noted: The tub area was repaired previously with 1/2 inch drywall . The remainder of the bathroom and house was 3/8 inch drywall. Drywall shimming was easy!