I have built a set of STi-oS 5 – sw , and a set of KE4-s 5 – sw irons with proseries R iron shafts, and a set of hybrids 4 – gap wedge with proseries R hybrid shafts. I play all three sets well. I hit the irons slightly higher than the hybrids, and distances are very close based on their loft with a straight to slight fade . What I see as differences in the raw shafts the iron shaft is 75 grams, hybrids 78 grams. The iron shafts have a torque of 4.0*, the hybrid at 3.2*. The weight isn’t much of an issue based on mfg. tolerance and can be balanced on Assy. Of club. I know that a lower torque will give a feeling of a stiffer shaft . My question is can the shafts be interchangeable without major issues ? Also, are there plans to start the school up in 2021 .