Either the KE4 MAX #5 iron or the FDI #4 iron could work. They both have the same 23 deg. loft, but the FDI is 6 grams lighter in head weight, so keep that in mind. I play the TS-1 irons down 5-PW, but have the FDI #3 and #4 and really like them. The MAX, from a head weight standpoint, would probably fit more in sequence with your set with regards to the club length. That being said you can always change the weight in the FDI to a little heavier to be able to match the remainder of your set. I don’t think there is a bad choice. The FDI is a shallower, more “driving iron” type of hybrid vs. the MAX which is simply a Ultra Game Improvement iron with a little more offset and larger face profile than the FDI.