Yes. I do all of the time. When you get your FHR confirmation via email, it ail have the Marriott reservation number on it. Just call MR and have them add your MR #. Its completely legit. You are paying the property. FHR is acting like a travel agent. MR has no problem with this at all. I get the 1k Ritz plat arrival gift plus points and elite night credit for the stay.