Dear Sir.
This is something that has been argued and debated amongst divers for as long as there's been upstream and downstream regulators.
And I wouldn't be surprised if this thread will turn in to a debate again, as it seems to be a topic that stirs up emotions.
To begin with, my personal opinion is that an upstream 2nd stage as the Jetstream or Xstream isn't more complicated than a downstream regulator. It's a bit different, yes, but not more complicated.
Secondly, if an upstream 2nd stage fails, it doesn't automatically means that it fails in such a way that it free flows and empties your tank. It can also fail "closed". It all depends on what causes the failure.
The most commonly argued reason why you should use an upstream regulator like the Jetstream or Xstream, is that they are quite easy to breath from. It requires little inhalation effort to open the 2nd stage valve and you get quite a lot of air.
The Jetstream 2nd stage has now been around for about 25 years and it's still a favorite among many divers who dive really deep on a regular basis. The Xstream 2nd stage is based on the Jetstream design and it seems it too is well liked amongst deep diving divers. But at the end of the day, it all comes down to your own personal preferences. Some like Poseidon regulators some don't and I respect them both.
I do not quite follow your statement about having to have 60 bar pressure in the tank, at 200 meters.
The Jetstream & Xstream 1st stage is set to an intermediate pressure of about 8,5 bar above ambient pressure. So even at 200 meters depth, the intermediate pressure is around 8,5 bar. So theoretically, you need to have more then 8,5 bar in your tank, to maintain the intermediate pressure. But in real life, you should not go below 20 bar tank pressure, as this might cause problems with a Jetstream or Xstream. Usually in the form of a free flow, as the intermediate pressure then don't have enough "umphfff" to seal up the 2nd stage.
I hope that this reply is helpful to you.
If you have further questions about our regulators, please feel free to contact me at any time at
jorgen.nilsson@poseidon.com