I kinda searched that mentioned 1,5 meter differences, it was not supported by any reference drawings I used. (nor it was mentioned where the length addition was placed.), The drawing that was ovgenoi seems to be always shown with same hull as the Pr.30k, just scaling it down won't give the correct drawing, since it screws other porpotions
The stern you migth be rigth, ...thougth this is the only picture of him with even sligth indication of the stern shape (you can see the beging of the transorm angle at the rigth bottom end of the pic)