I have a 16" A2 rock river upper dpms lower. Its a fixed carry handle and I want to go with an eotech 512 or 517 red dot holographic. From what I can find I need a cantilever type mount to bolt to my carry handle and then the pictinny rail would extend forward over my forearm grip and the red dot mounts on that. Is this correct? Also can I still see my fixed iron sights through the red dot mounted this way?