Thanks IslandAlchemy!
I agree but I was recently sailing with another boat and it was very easy and fast to depower the mainsail letting the kicker loose, the boom went up when arriving at the anchorage spot and it seemed me interesting.. I am unsure (I was at the bow and didn't ask later) if they just released the kicker or they just use the topping lift.. Anyway, the problem for doing this quickly with a rigid boom vang is that before to use the topping lift you have to release mainsheet (that should be loose in a slow approach) but also the vang.. Not sure, just looking for a way to make it faster...