"I don't know how long the set of 5x 2-56 screws and blind nuts are supposed to be."
Sit your Graflok back against the adapter plate and measure from the base of the screw hole (where the bottom of the screw head mates with the screw hole) to the bottom of the blind nut when installed on the adapter plate. It will probably be 3/8 to 1/2 inch.

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If Bert Saunders phone and email are no longer active then he is in an assisted living facility or no longer with us.