I have an AR I just put together and it has a fixed front sight and a fixed rear Troy Battle Sight. I also have an Aimpoint ACO that I can put on it. The ACO is an absolute cowitness optic and I'm thinking that may leave me with a pretty cluttered sight picture. Is there a riser I can get that will work with the ACO and get me to a lower 1/3 cowitness? I really don't want to have to buy a flip-up rear sight to get it out of the way.