This patch contains 3 different sub-patches related to releasing held items: "Release while Spinjump fix", "Easy / Disable Mid-air Patch", and "Release into Solid fix". Two of the three are bug fixes, and all of them can be disabled, as well as each sub-patch having various customizable options.
The first sub-patch removes some of the jankiness with releasing items during spin jumps. Instead of releasing items in a random direction, sprites are released in the direction held on the controller. In addition, items released while spinning can be set to release from the center of Mario instead of one of Mario's sides.
The second sub-patch alter the release physics to make mid-air shell jump easier or harder / impossible. Essentially, it alters the speed and interaction frames of an item that is kicked while Mario is turning.
The third sub-patch fixes the issue where items released into a solid wall will clip upwards. If a released sprite is detected to be in a wall, The sprite will instead be released next to the wall.
Read the README.txt! If you have any concerns about the patch that aren't addressed there, feel free to PM me.