jimbob wrote:They do not give you a centering arrow though to know where the weight really is on the scale.?
True which is why it is hard to set exactly without a manometer (at least for me), although 'exactly' is probably not necessary. But how level and plumb your baro is will affect the accuracy of that scale and having a manometer takes the guesswork out of it.
Also, if you put it in on a diagonal section or in an 'unrecommended' bullhead location like mine, how accurate is the baro scale.