I am enjoying the comments here and on the other thread (which I didn't know about before I started this one--sorry). Like many passionate people who frequent this forum, I like to argue. Besides my propensity to swim upstream, I have no experience w/ valves down except for a childhood experiment w/ firefighting rig in the lake (My Dad still doesn't know about that) and later with that High Pressure norwegian rig w/ the 1st built into the manifold (4,500psi). A great deal of the criticism of valves down is due to thinking of it as just another "application" w/in an established "system". I'm questioning the "system". If the idea has merrit then it will be built from scratch, not kludged from the valves up kit. I have so far been able to manage my valves. It is an uncomfortable manoever that many here seem to love just because it hurts! If I'm injured, tired, confused or panicked then why in the world would I want using my valves to be almost a stunt?
One major question that we probably need to address is just how important is access to valves?
Single tank sport diving maybe not very. Tech diving w/ doubles, isolator etc. it is much more important (but not routinely, mostly just during malfunction).
Another Question: entanglement The picture posted of a valve guard w/ isolator pointing to the back is potential for trouble. It also doesn't need to point back, it can point down w/ different guard design. Also, what could possibly be more vulnerable than the valves up? Isolator pointing at direction of travel, 1st stages of various protrusions etc.
hose routing: Now that we have so many using 7' hoses etc. I just can't see this as a problem. Finding the optimum will require thought, but it just can't be a serious problem, can it?
Dealing w/ Kit topside transport, rigging etc. is where a lot of us see the biggest problem. But even this is because of convention. We lug our tanks around by the valves (never the manifolds--yeah right!) and waddle around the deck. Is this a good idea? Valves down would probably make attaching handles more necessary but then would that be a good idea regardless?
If you have to choose, do you want maximum efficiency IN the water, or ON the boat? I realize this is not retorical. I have most of my frustration out of the water (loading, moving, rigging, trying to get off my knees on the dive platform w/ out some teenage girl having to help me up!).
All of this is pretty much theoretical for me so please take it in that spirit I have no qualifications on this issue, it's just a mental exercise. Even so, without mentioning names

I'll bet a pony bottle that the most ardent opponents of Valves down on this thread, could solve all the problems they and others have stated! In fact, they would be the very people who would come up with the most bullet proof solutions.
Again, I have really enjoyed the discussion/argument
