You can set a new hitbox using the 'Set Actor Collision Bounding Box' event when sonic is set to his crouching state.
The GB Studio Discord is really good for fast responses to these types of questions, I'd join the discord if you haven't already.
I don't seem to have that event, is it in a plug-in?
You may not be using the most recent version of GB Studio? It's a new event that is not currently listed in the GBS docs.
I'm using GBStudio 3.2.
I think there is a plugin that will help you change the collision bounding box in GBS3.2. If there are any other issues, its best to ask questions on the GBS discord.
