Completely removes the status bar, along with the item box and the timer. There's an option to internally reenable the coin counter and getting 1UPs every 100 coins, otherwise these are disabled as well.
This does free up space on the screen for layer 3.
You may also use the area previously occupied by the status bar data/code as free ROM space (some of it is already used by this patch).
The screen... it looks so different.
You really want to use this in combination with a power-down patch though. Without reserve item, it's kinda nasty to always go back to being small after one hit.
Keep in mind to remove the necessary lines from the patch when using power-down though