I had this similar experience with Xflex $tapers. S+ is ideal for me. Sadly, not many OEMs offer that flex.Landing angle should be close to 45 degrees which that is, peak height with 6iron should be around your swing speed which it is, spin is good. Numbers are great. Question is can you swing the heavier shafts over a full 18 holes? That’s something you’ll have to decide. I was in this exact same situation, but I found my self tired when from swinging at fitting (trying to create the best numbers possible). Realized to myself I rarely play a iron shot to it’s maxed out number or swing all out. I ended up with kbs stiff 120. Like the feel better and if I want to step on one they are still stable enough to do so. I think the only other thing to consider is not the flex, but the weight of the shaft. The weight may help in your swing sequence.