A mobile support cart has one or more extendable and foldable arms to position one or more monitors or devices mounted to the extendable arm. The arm is mounted to a vertical column that is supported by a linear rail system providing vertical guidance. An adjustable counterweight carriage rides on a second rail set and is connected to each column through a chain and pulley. Each chain and pulley is fully redundant with two chains attached to discrete mounting points on each counterweight carriage and to each column. The amount of counterweight applied can be adjusted within a given load range by adding additional plates/ballast to the counterweight carriage. When the load on the arm(s) are fully offset by ballast on the counter weight carriage the arms and payloads reach a “neutral buoyancy” condition. The system maintains the position once an operator has released them.