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

Coatings solve that issue. Running CuBr is one thing, finding someone with the PPE to machine is it another.

DLC and CrN would be advisable. Either one makes the valve job hold up exceptionally well with regular stellite seats.

*if* a person was wanting to run uncoated valves a company outside of Milwaukee makes a material called Moldstar90 that is commonly used for valve seats in Ti valve engines.

Have you priced out Ti valves yet? Two Ti intakes is more that one set of Ferrea 6000 SS valves. It seems like you would pick up more with a solid roller cam than spending 3k on valves, lash caps, retainers, locks and a new set of springs. All of the will more than likely have to be changed.

That said the reason for lightening the valve train with is typically to gain RPM, extending the powerband beyond where a steel valve deal would experience valvetrain instability. Like >7500rpm, which I will guess this engine won't see.

My reason for going Ti valves in our 511" low deck is 8800rpm.

RPM isn’t nearly as important as overall valve length and head diameter. There is no arbitrary RPM where you switch from stainless to titanium valves. Or even when you switch to smaller stems. There is never a negative going to a lighter valve.