I’ve had a Steadicam JR for many many years. (very similar) It’s AWESOME for shorter durations, maybe a few minutes max. Much past that and your hands/arms get tired… after a minute rest you’re ready to go again, but forget holding without a break for a extended shots, like you might with a shoulder-mount. Hold a 10 lb weight steady in front of you at a 45 degree elbow bend & see how long you last…. it’s about the same. Don’t let your elbow rest on your torso – that’s cheating.