[pat fish]

Hi Frank,
Of course stress is not the only factor. And of course it can be unfavorable also. But shutting of peripheral perfusion is mainly triggered by activation of sympathetic nervous system (stress) or coldness I guess.
What you say is: initially elevated CO2 levels wouldn't affect peripheral constriction too much. That would correspond to Sebastian's thesis of no preparation at all for a strong DR, am I getting it right? If it is true that a bigger spread of CO2 between initial levels (not alcaline though..) and elevated levels is contributing more to a good DR than a smaller spread (start with elevated CO2), this would corroborate your advise of starting with normoventilation.
What I believe is: Getting a good DR isn't as much of a topic in constant weight as it is in dynamics. On a good sinking phase in constant weight, the increasing water pressure in head down position helps a lot to trigger good DR.