I think shoulder mounting is underrated. Shooting from the shoulder is a bit of a lost art, and it's nice to see the FX6 can still work well that way when rigged properly.
You’re correct with the payload and I can successfully balance it. Can’t tilt down all the way before it gets thrown off but will tilt down 90%. We have heads rated for up to 17lbs that still don’t balance as well as the FSB4. A new head is on the list but not something needed asap. When we rent larger camera packages we rent bigger sticks obviously as well.
It’s really not as front heavy as you’d think with the larger 180w vmount but it’s not centered up. My issue is some shoulder rigs in the past that I can get everything on the center of gravity sits too high for me. Luckily I’m not shouldered up on a show for a full 10-12 hours, for the work I do my longest take is usually 10-15 and I don’t fatigue. What setup or pad do you suggest?