I bought irons off the shelf. I hit them in a net to measure swing speed more than anything so that I went with the right shaft flex. I didnt have time to have the lie angles adjusted from the shop I got them from as I purchased them overseas and was leaving within a few hours. So when I got home, I went to a fitting station, I hit balls with lie angle tape on the soles and then had them bent to suit. Provided the shafts are ok for you, it will be a fast and inexpensive exercise. Mizuno do offer a fitting cart system that will help you select the right shaft for you should you need to change, but that will be an expensive avenue, but depends how much your investment has already cost you and how much you are willing to spend.
