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What you are calling fingers I was calling support arms.
O.K. I *guess* that it could be used that way -- but I would have designed it with something as part of the device to control the tilt of the fingers in the basic linkage, not depending on a cavity which may or may not be available in the piston.
And there are too many likely lumps inside the piston to really allow it to work reliably. A piston is not typically as empty as a coffee can. There are the bosses which carry the wrist pin bearings and keep the connecting rod centered.
But unnecessarily complicated to use.
I still think that it serves some other function.
Enjoy, DoN.