Quoted TextPrecisely, it appears to be the case of making a model of something without understand what the subject actually is and how it works.
If you are just making some boxes, you don't realize the issue... if you are making fin carriers odds are much higher you realize they need to carry some fins!
From Chris F's and the Tankograd book mentioned previously, it appears that there were 3 different M-number designation for the fins and at least 2 different sizes, but neither of the 1:1 sized fins would fit the kit fin cases!
They def dropped one here....
To my knowledge there were only two sizes of control surfaces.