I drilled and tapped my dust cover and just threw on an extra metal rail I had laying around. I used some VERY short stainless screws and locknuts underneath as well (from Lowes)....and used loc-tite to boot.
I have a Bushnell TRS 25 red dot mounted on it (this is a Saiga 7.62). This set up is ROCK SOLID. I used this rifle like this all of last year shooting 3-gun and I have NEVER lost zero with the red dot and did very, very well with my scores!!