Kind of confused as the heading said TaylorMade M6 iron. Are you needing an iron shaft or a wood shaft recommendation? I can’t find any information about an Atmos Red 5 iron shaft. Generally “Red 5” would indicate it is in the 50 gram range in weight. If the A flex feels too stiff, you could try lighter, but options that would be noticeably lighter are not that plentiful. I would suggest going lighter, if you can, and to possibly an L flex, or R3 flex, or Light flex, depending on the manufacturer and model. Since I don’t have the Atmos Red 5 info in my database I can’t really compare the overall flex profile with other options, so I can’t really give you specific shaft models.