I did a similar mod on mine, and it greatly helped on the low end, the reason that the Oktavas get such bad press (of course, there's still people in the taping communities out there that bad-mouth work with the MC012's -- I used to get it all the time). I made some tapes that I consider extremely impressive for the price... I moved over to Earthworks SR77's, and while the price difference is noticeable (I really like the 77's overall sound), the money for the MC012's -mod or not - is still a great deal for beginners.
I went from AT853's to the MC012's and kept them for over 3 years...