An adjustable seat support assembly comprising: an elongate flexible beam spring having a flexure that changes when an effective length of the beam spring is changed, the beam spring have a proximal end and a distal end; and an actuator that changes the flexure of the beam spring by changing an effective length of the beam spring, the actuator comprising an inline slider mechanism disposed at the proximal end of the beam spring, an elongate substantially rigid beam spring flexor extending outwardly from the inline slider mechanism longitudinally alongside the beam spring from the proximal end of the beam spring to the distal end of the beam spring, the beam spring flexor connected to the distal end of the beam spring and displaced by the inline slider mechanism longitudinally relative to the beam spring to change the amount of flexure of the beam spring in adjusting an amount of support provided by the beam spring to a seat occupant, characterized in that - the inline slider mechanism comprises an inline slider cam-follower mechanism having a rotary cam that displaces a follower yoke riding on the cam, the beam spring flexor extending outwardly from the follower yoke displacing the beam spring flexor substantially in unison with displacement of the follower yoke, - the follower yoke has a sidewall bounding the cam with a follower radially inwardly extending from the yoke sidewall that rides along an outer profile of the cam, and - the cam has a radially stepped profile with a plurality of circumferentially spaced apart stops (170, 172, 174, 176 and 178) which releasably receive and retain the follower therein in a discrete beam spring adjustment position. an elongate flexible beam spring having a flexure that changes when an effective length of the beam spring is changed, the beam spring have a proximal end and a distal end; and an actuator that changes the flexure of the beam spring by changing an effective length of the beam spring, the actuator comprising an inline slider mechanism disposed at the proximal end of the beam spring, an elongate substantially rigid beam spring flexor extending outwardly from the inline slider mechanism longitudinally alongside the beam spring from the proximal end of the beam spring to the distal end of the beam spring, the beam spring flexor connected to the distal end of the beam spring and displaced by the inline slider mechanism longitudinally relative to the beam spring to change the amount of flexure of the beam spring in adjusting an amount of support provided by the beam spring to a seat occupant, - the inline slider mechanism comprises an inline slider cam-follower mechanism having a rotary cam that displaces a follower yoke riding on the cam, the beam spring flexor extending outwardly from the follower yoke displacing the beam spring flexor substantially in unison with displacement of the follower yoke, - the follower yoke has a sidewall bounding the cam with a follower radially inwardly extending from the yoke sidewall that rides along an outer profile of the cam, and - the cam has a radially stepped profile with a plurality of circumferentially spaced apart stops (170, 172, 174, 176 and 178) which releasably receive and retain the follower therein in a discrete beam spring adjustment position.