I put my Widepan EOS/Graflok adapter on my Sinar P set up as a 4x5" with a bag bellows, and I can go as short as 135mm using a Sinar/Technika adapter board and a lens on a flat Technika board. So with a recessed Sinar lensboard, shorter should be possible, depending on mechanical factors like clearance for the rear cell of the lens.
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