I recently added a Maggie to my 2012 R/T. I want to go to a colder plug (2 steps). It was recommended to me by Arrington that I use LZTR7AIX-13 (5107). I believe this is a "tapered" seat plug and not a flat seat plug. NGK strongly stresses that the 2 are not interchangeable (tapered / flat). 2 questions: (1) looking to confirm that we do have "flat" seat blocks (2) anyone used/using this plug...or have recommendations?