1.  Kevin, from my point of view, the center isolation valve is an important 
piece of gear that provides for preventing an emergency.  This prevention 
can not be duplicated by any other means, so the valve is not a redundant or 
extraneous piece of equipment.

2.  Like many pieces of required safety gear (e.g. second 1st stage and 
second 2nd stage, etc), you wouldn't delete them from the rig based on "the 
hogarthian principles" just because you don't normally use them.  Why not? 
 Because they are deemed essential.  So is the center isolation valve.  The 
use is (as you know) to isolate a failure on one side that can not be 
isolated using the applicable valve supplying the 1st stage on that side. 
 Since this isolation can not be performed in any other fashion, this valve 
is a requirement.  And by only having one, instead of two isolation valves 
(one for backup) you are practicing the "minimal approach" based on the odds 
of encountering a compound failure (i.e. a failure on one side and a failure 
of the isolation valve).

3.  That's the way I thought about it when I switched over to Hogarthian 
about a year ago.  I would suppose that there are others on the list that 
will be able to provide more reasoning, and perhaps be more eloquent, but 
that's my $0.02 worth.

DIVE SAFE!

Dave M.

****************************************************
* Dave Montague                                    *
* 94-1088 Kaahole Street                           *
* Waipahu, HI                                      *
* Work Phone: 808-474-5643                         *
* Home Phone: 808-678-2816                         *
* Work E-Mail: dmontague@c9*.ll*.nu*.na*.mi* *
* Home E-Mail: cavedave@la*.ne*                   *
****************************************************
           OOOO
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   -==0 oooo
"Cave divers do it with deeper penetration"!!!
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