At what point would you step up to ferrea hollow stem valves

Great points, I'll be staying ss & when I go to solid roller I'll get some beehives & ti retainers because I'll still only hit 7k

That is a good plan. I might check out "TensileMax" retainers sold by Manley. It is lighter than tool steel/CM, strong and less expensive than Ti. It is commonly used in endurance type engines.