I'm using one and they fit well albeit a little blocky looking.
The aperture extends back enough to be hit by the bolt on the rearmost ring mount so it needs to be mounted on the more forward of the two rear ring mounts. I swapped the front bead for a sourdough type blade but don't remember the height. If you still have the factory rear in place, install the NECG and see if it aligns with the OEM sight picture and go from there.
