Custom Entity Hitboxes - Length and Width

Hey folks,

I have been having issues with a custom mob I created due to the inability to set separate length and width dimensions on the entity’s bounding box. I have seen some other forum posts with similar concerns, but they don’t appear to have received solid answers. I am aware that MCreator forces cube-shaped hitboxes, but I would like to know if there is a way to manually edit the code to get around this restriction:

• Specifically, which file would I need to edit and where should I find it?
• What changes would I need to make to the code itself to set a rectangular prism shaped hitbox rather than a cuboid one?
• If this is impractical or cannot be done, is there a way to set multiple hitboxes for different parts of the body, as is the case with the ender dragon? (see: https://learn.microsoft.com/en-us/minecraft/creator/reference/source/vanillabehaviorpack_snippets/entities/ender_dragon?view=minecraft-bedrock-stable)
  
  Would be very grateful for any help, thanks for reading!