Guys...somewhere in the dim dark past I have read about "spring loaded steam throttle cushioning" ..mounted between the servo & the throttle

So even with proportionate RC control trimming of the servo arc of travel [stroke].....the "spring loaded steam throttle cushioning" ensures full desired stroke can be achieved....also with positive steam shut off.....but prevents any additional movement from what ever force or applied torque that could cause damage to the throttle internal mechanical stops or weakest part being the linkage arrangement

Am sure it was two captive springs that work in a push pull arrangement ......from memory the original concept came from Sandy Campbell....but cannot find any reference to it via Google

Any thoughts appreciated    ... Derek

Something like this?

Hi Derek
You can build that easy by yourself! Just 2 springs from a lighter, and two pieces of brass tube with cut in thread, that`s all.
Regards
Gerhard

There is an even lower-tech option Derek, an omega wire.  If the operating rod is fairly thin and elastic you can put a Ω shaped bend (a similar shape to an expansion bend in a steam line) in the operating linkage that will stretch or compress when full travel is reached.

All the best
Brian

Thanks Guys.......now on the right track with this ....am also considering incorporating an ACTion P96 slowdown/positioner to control the actual steam regulator   .... Derek