Yes there is a published...
limit for tq in feather. It is ten pounds and it is to prevent bending the propeller blades. Says so. Try reading your SBs, because I think it is there also but I don't have it in front of me at the moment. I do have an "old book", but it is for a 300, but it‘s not in front of me either.
You do not get 51% +1-0 until you take it out of feather or its rigged wrong. I don't like sending oil pressure to change the propeller pitch until the engine is at least stabilized after start. I prefer all that oil pressure for the engine and gearbox during start.
However I don't do this anymore and I would have to refer down to ops or maint for any changes. I do appreciate your info.