One thing to consider is the "unique" vords as compared to those that repeat at least a few times.
Unique vords don't necessarily follow the [exact] same structure.
Note that unique vords can often be broken into two vords that do follow patterns similar to the vords around them, just as removing EVA-P from the beginning of paragraphs (treating them as a special case) often yields vords that follow regular patterns.
Also, something I've noticed is that EVA-ch -sh (which you've classified in the "c" group) are more positionally flexible than many of the others and MIGHT belong in a class of their own (or differ in some other way).
Unique vords don't necessarily follow the [exact] same structure.
Note that unique vords can often be broken into two vords that do follow patterns similar to the vords around them, just as removing EVA-P from the beginning of paragraphs (treating them as a special case) often yields vords that follow regular patterns.
Also, something I've noticed is that EVA-ch -sh (which you've classified in the "c" group) are more positionally flexible than many of the others and MIGHT belong in a class of their own (or differ in some other way).