I have a FF3 on a CORE 9L ported. You can co-witness the sights on the Burris. There is just enough of the sight visible to effectively do so if that is an requirement. Personally this is strictly a open gun for me, and I have no need for the iron sights, and may remove them entirely if I can find a dovetail to fill the space. I also run a FF3 on my .22 open gun. FF3's have been good to me, taken an extreme amount of abuse, held zero, easy to adjust sights, and simple battery replacement for the one time I've had to do it. Typically during the course of a summer at least two days a week the sight stays on all day. Was looking at an RMR and may still get one but was able to get two FF3's for the less than the price of an RMR. I am a Leupold fan-boy but ruled out the Delta point, it was either the RMR or the Burris.
Good Luck