I just read Joe Citelli's article in the current issue of Underwater Speleology titled "Breathers, Buoyancy and Caves." In talking about weighting for rebreather divers, Joe says, "Ideally, a properly weighted diver should be slightly positive on the surface and need to make a small effort to descend the first five or 10 feet, after which gravity takes over and he should begin to drop relatively freely." Let's ignore the fact that gravity has nothing to do with it, and its actually the compression of air in all air spaces that makes descent easier. My concern is with the "proper" weighting being slightly positive on the surface.
As rebreather divers, shouldn't we be aware of the possibility of bailout? This is true in cave, wreck or open water environments. Even if you drop bailout tanks as you use them up, your buoyancy is going to change during the dive much more than in a non-bailout situation. I think the ability to hold a depth at the end of a dive is critical, whether its a deco stop or staying off the ceiling. I'm not in favor of gross overweighting, but I think Joe's suggestion is not necessarily wise.