Are there any issues with doing this?  I know it will physically mount, but has anyone done it or had problems with it (something coming loose, losing zero, etc.).

Also, can you still use the iron's with a compact acog mounted?  It looks like there's a hole in the base of the M16 mount, but I can't tell from pictures.  A buddy would like to mount a 1.5x16 on a handle.  It would be a mostly-permanent set-up.

Thanks!

i have one. hasn't lost zero and never had any issues. I love this setup.

you can still use Irons.

Here is mine.

It works great.
Mine is a 2x20.

mine works great too (TA44-5)

with the ARD mounted you can't use the iron sights, it needs to be modified