I prefer manual, I made this so I can't forget! Actually the main reason was so the board could go in a board bag in a hot car and I could rest easy knowing it wasn't going to breathe in the humidity. Some silica beads are in there for good measure. Manual vent in for sailing, this attached when not - best of both worlds.
Before everyone tells me I'm mad for attaching some big object to a board's vent, it is 3D printed and the vent screw layers separate very easily, any knock or over tightening the thread snaps well before the board would feel any stress.