For the past 8 years I have been gaming a set of CER 851UM irons w/ Xcaliber graphite shafts. I love the overall design of these heads, especially the combination of high MPF and thinner topline. Sadly, they are getting pretty beat up and I am getting the itch to build something different. Which of your current designs would be the most comparable to my 851UMs? My thinking is it might be the ST-i head. If so how will it be different or the same as my present irons.