Sub Drivers boat is a Kehrer hull not an Engel.
I'm not really a scale buff, and certainly don't know much about Russian subs, but I do know that the Engel plans are off, and there are a lot of differences between different Typhoon boats.
I think most of the limber holes are actually scribed in the wrong position on the Engel. Ramesh knows a shedload about this boat, and there is a chap in France who did a stonking build of one, and altered lots and lots.
All depends how particular you are about authenticity.