help with shaft.
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The Aerotech SteelFibers would be worth checking out. It's technically not a graphite shaft (they are carbon fiber), but it has some of the same benefits and will handle any swing speed. They tend to play a little stiffer than they are rated, so be aware of that. In terms of feel and performance they are definitely a good option.
I play that shaft in my hybrids, and it's a great shaft, but one thing to keep in mind is that they recommend trimming those shafts from the butt only. Typically parallel tip iron shafts are tipped in 1/2" increments.
I play my c tapers soft stepped, I tried them straight in and they required a lot more loading to feel right. Though I can handle most x flexes in all my clubs, the c tapers play about half a flex stiff compared to dynamic gold. The X100 is about the same for me as the soft stepped C taper. My swing speed is higher than yours though, so there's a half to full flex difference I would imagine.
If you go with the aldila RIP, I play it in 2 of my low lofted hybrids but the iron shaft itself I haven't tried. The X in the Rip alpha hybrid plays similar to my soft stepped X stiff C tapers which are the same as the S+ straight in. Launch and spin were both similar, and control was solid. So I would recommend you soft step your irons and maybe play a tipped S flex if you try the RIP alpha to match that.
Other than that, it might be worth considering adding like 2 hybrids. If graphite would benefit you, then it's likely it will help the long irons the most. I haven't tried any of the graphite iron shafts, but honestly it won't cost nearly as much to try soft stepping first since you will probably only need to buy one shaft. It's not a difficult job to do yourself if you've done any clubmaking and don't want to spend the money. Hope that helps.