Thanks for the good info! I don't have a CORE but I was considering getting the M&P Pro ported slide kit that comes with a CORE system in the slide with elevated irons (as well as other features).
I ended up getting a DueckDefense RBU since this has the iron sight built in to the plate. This further elevates the DPP above the bore axis but that was less of a concern than having irons cowitness the sight. Plus this saved me the $400 from purchasing the S&W slide kit as well as the Leupold CORE specific mount plate.
Took it out to the range last night to zero and test it out. So far I'm extremely happy with it!