You should only nade at enemies you can see and have a realistic chance of hitting. Although you can see enemies on your radar on the level above, there is no reason to nade up. Nading from the bottom of the bridge to the top would be classed as nade spamming. While you are a passenger in a hog, remember to be mindful of where you are throwing nades, and when. Don't inconvenience your driver or other teammates. They should never have to avoid your nades. I would avoid doing this in a server.