If you are flying of a hard surface runway it is especially good to have a slightly negative angle of attack when all three wheels (remember this is a trike geared plane we are talking about here) or the plane will often be adversly effected by any wind while taxing and can even jump off the ground with insufficient flying speed. putting elevator in to hold the nose wheel down while taxing doesn't help as the plane can not rotate down enough to kill any excess lift. This is especially important for the less experienced flyers so, for best and easiest experience, have a negative angle of attack when a trike geared plane is at rest.