You are correct in that there are not many hybrid specific shaft options in 50 grams. The XXIO Hybrid is a .370 hosel, so you can use an iron shaft. Hybrid specific shafts are basically iron shafts. We use them in hybrids all the time. The head weight of the hybrid will determine how you would trim the shaft. For example, if the head weight of your #3 hybrid is 234 grams, that is like a #2 iron head weight, so you would trim the shaft tip as if it was a #2 iron, then trim to your playing length fro the butt after installation. You might look at the Aldila NV iron (61g option in R flex) and the Fujikura Vista Pro iron (62g option in R flex).