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>>>I will admit it, on two occasions I have needed to use my pony bottle. Both
>>>times were in no-deco situations, and I didn't have enough gas in my tank
>>>to complete my safety stop without draining my main tank below 500 psi.
>
>Or maybe everything would've come out okay -- I wouldn't've been bent and
>my tanks would have passed inspection for another year, and 


From the above comments it would seem you are concerned about "damaging"
your tanks if they should happen to go below 500psi. If you completely
drain your tanks there is a chance that water may enter the tank, which
clearly is not desirable. You do not however need 500psi for this purpose.
As long as the tank pressure is slightly higher than the ambient water
pressure water will not enter the tank. For a shallow stop you won't need
much pressure at all, probably 50psi would be plenty. In fact if you are
still able to take unrestricted breaths off the tank (even if it is very
low) then the pressure inside must be higher than the pressure outside and
water will not enter. So in fact 500 psi was probably more than enough to
complete a safety stop without using your pony.
	If fact some people argue that there is little point in getting back in
the boat with 500psi still in your tank when you could have used that gas
to extend your safety stop and therefore decrease your risk of bends. (This
of course would only be advisable in "uncomplicated" circumstances where
you are unlikely to need the 500psi to extract yourself from some other
situation)

PS - I otherwise agree with your comments on ponies! I use one regularly
and can see no point whatsoever in lugging around twin tanks on
recreational dives where a twin tank and a pony will provide you with all
the redundancy you could ever want.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Ocean Internet - "The Quality ISP"
http://www.ocean.com.au/info.html

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