An agricultural vehicle (10) includes a chassis (11) and a header (100) carried by the chassis (11). The header (100) includes: a header frame (101); a cutter (110, 910) movably coupled to the header frame (101); a reel arm (123, 525, 535) pivotably coupled to the header frame (101); and a reel (120) carried by the reel arm (123, 525, 535) and including a plurality of tines (121). The agricultural vehicle (10) is characterized by a variable displacement fluid cylinder (200, 600) including an interior chamber (210, 610), a first piston (220, 620) linked to the reel arm (123) placed within the interior chamber (210, 610) and a second piston (230, 630) placed within the interior chamber (210, 610), the interior chamber (210, 610) defining a shared volume (211, 611) between the first piston (220, 620) and the second piston (230, 630); and a piston driver (300, 640) linked to the cutter (110, 910) and configured to translate movement of the cutter (110, 910) relative to the header frame (101) into displacement of
