the 250 quadcopters are great to take along on hikes for filming. but there is still room for further miniaturization without having to bullnose the 5 inch propellers. the 210 class appears to be pretty much the minimum that makes sense. so here is a homemade 210 class quadcopter.
the size offers another advantage, at least when flying in switzerland. our laws regulate rc planes/multirotors above a take-off weight of 500 g (= 1.1 lb) more stringently. with a 210 size quadcopter it is possible to remain below this limit without having to sacrifice a camera for filming and the fpv equipment.