With the riser installed, this sits at lower 1/3rd co-witness. This means that the iron sights will be visible through the scope view, however they will sit below the reticle, so they will not interfere with use of the scope.
I have this mounted on a S&W M&P II with an A2 fixed front sight. You can see right thru the front sight without any significant interference. Not an issue.
I have exact issue on my AR. Front site is bearly noticable. no problemo. awesome optics.