I guess I haven't seen much bouncing because I rarely get to the advanced type artillery before the campaign is over, and even if I do get it I generally don't build much because my empire is so spread out by then I need to move armies around quickly. Funny about the uphill shots though, I remember from Rome preferring to shoot downhill to get good bounces, i guess it depends on the range, when shooting uphill you need to be close so the shots will be rising and following the upward slope of the hill when they hit, and far away when shooting downhill so they will be falling, in order to reduce the angle of impact.