.02 worth of experiences
A "rod vang" was factory standard on our '88 boat. I recall thinking that if I known how convenient that was compared to the topping lift line on our prior boat I would have installed one that former boat!
The gas return piston in that old vang had lost pressure by the late 90's, and I replaced it with a new one that uses springs for the return force. Still have it and like it.
It's great not have the old topping lift line waving around and catching on batten pockets. (That problem is curable, mostly, with a lower section of bungy cord led to a small cleat on the boom.)