hoshi

I'm using a curve one that is approx the same length as the original mirror in the car.  This way it gives me more view and not having any problem flipping down the sun visor.  I still do shoulder checks all the time.  I found that a wider angle mirror gives me better observations to plan ahead for things like lane changes.

I think once you get used to the view the curve type is not a problem.  It is just like the case of right side side-mirror which is also not showing the "true" distance.