As described in SVC-1972, VEHICLE_FLAGS_HOVER_UP_ONLY does not result in behavior consistent with its original documentation. However, its current behavior has become (to quote Andrew Linden) a "misfeature" that must be preserved because too many vehicles depend on it. I'd like to propose two new flags for vehicles. One would actually do what the old flag didn't: cause hover to push up only while not ever causing any downward push, essentially establishing a "flight floor" for the vehicle. This would be extremely useful for craft like a seaplane, where it should be able to fly free, but upon descent to a certain level, not descend further but merely bob a bit, hovering at that height until taken into the skies again. This could be called VEHICLE_FLAGS_HOVER_UP_ONLY_FIXED, or maybe just VEHICLE_FLAGS_HOVER_IS_MIN or HOVER_IS_FLOOR or the like. The second flag would do the opposite: cause hover to only apply downward force, never upward force, establishing a "flight ceiling" for the vehicle. This would be useful for craft like a submarine, which should have a full range of 3D movement below a certain height, but be prevented from going above it, just bobbing a bit when it reaches the max. This could be named something like VEHICLE_FLAGS_HOVER_DOWN_ONLY, VEHICLE_FLAGS_HOVER_IS_MAX, or HOVER_IS_CEILING or anything along those lines.