Weight on the front is fine, but only if it doesn't move around.
The Minoura I have puts most of the weight over and in front of the front axle. If you turn the bars fast, it tries to keep turning them when you stop. You do better hanging bags off the side like lowriders, but then sometimes I have grounded them.
My latest experiment is a rack that mounts to the top tube, but it's not finished yet.