I found that no matter what you enter for an enemy's dimensions, it will take the dimensions of it's enemy type.
Will the dimensions field be functional in 2.5? will you be able to create your own size enemies regardless of their enemy type (for example: having an enemy type Aquamentus that is 6 tiles wide and 4 tiles high)? If not, this is something I'd like to point out.
(in case anyone's wondering, I was trying to make a "Big Core" from Gradius.)