I am curious. Why would a piston first stage need "often tuning" to maintain performance?
My Sherwoods are very simple. The only first stage "tuning" I am aware of would be to remove or add a shim if the IP drifted too high or too low. Essentially you are compensating for the spring providing too much or too little force. As it ages, I assume the spring may start to weaken and not provide enough force - so you eventually might need to add a shim. My 30 year old regs are still using the factory configured shims (2 of the allowed 3).
Maybe I am missing something?
I do realize that my regs are not Ferrari's. Do Ferrari piston regs have more fiddly bits?