They aren't final; indeed, they're what you've been saying all along. Repeating them doesn't make them more true (or less false!) than they were before.MHK:
The concept of pressure gradient isn't in dispute either. What is in dispute is whether the issues you claim to be addressing have a real, measurable effect on divers that make mitigation statistically significant in any way at the depths in question.
There is no doubt that at 200', for example, trimix is a good thing. That is not the point under discussion. The point under discussiion is whether it has any value (other than emptying your wallet faster) at 70'.
More misdirecton Kane. The "naysayers" are asking for anything beyond anecdotes that provides evidence of statistically-significant benefit in the range of 100-120'. You've been asked for it on SDN, and now here, and you keep sidestepping the issue and demanding instead that others prove a negative.
That's not how science works. You prove positive things, not negative ones. As anyone who has any kind of background in the scientific disciplines knows, proving a negative is extremely difficult, as you must eliminate all other possibilities. Proving the converse positive is much easier - if its true, of course.
Actually, that's only half of what's in dispute.
The other half of what's in dispute is that the "our position" (thank you for actually identifying this as an official GUE thing too) is the hypocrisy of teaching and certifying someone to do a thing that cannot be responsibly done with the equipment demanded for the class.
No responsible person would do a cave dive (even one with only very limited penetration!) with a single-cylinder, single-orifice tank. Why? Because you have no breathing-gas redundancy, and even when dove to thirds you could find yourself out of gas before you and your buddy can exit. This is true irrespective of the SIZE of the single tank.
The same principle applies to this class, IMHO. Diving Helium-based gasses requires more discipline in ascent profiles. Exactly how much more is the subject of some dispute, but that additional discipline is required is not. Indeed, GUE will not issue the card if they are not convinced you can manage this additional discipline.
This, effectively, means you are in an overhead environment. This is true any time you have had to discard a CESA as a valid response to an emergency, reserving it for the last-ditch column in which the only other choice is certain death.
Since this is an overhead environment, appropriate equipment should be mandated for the class. Kane argues that requiring doubles for such a class is insane. I retort that there are other options, such as dual-orifice valves on large single tanks (e.g. AL100s, HP100 and 120 steels, etc.) or the use of a pony bottle.
Indeed, some form of complete air-supply redundancy has become required kit on many NE dive boats. These folks know something that Kane doesn't? Or is it that GUE simply doesn't want to "limit" their class to people who will make the appropriate investment in both training and money to utilize what they have learned?
There is more than one point in dispute, as I have repeatedly pointed out. Outside of the range where some form of air supply redundancy is, IMHO, mandatory, I argue that Heliox is without benefit. That would be for dives of less than 100' in depth.
For dives between 100-130' there may be some benefit. However, at that depth IMHO additional equipment requirements come into play. As such that equipment should, IMHO, be required for the class, since diving at those depths "more safely" is the entire point of the class.
And now, in closing, you add a gratuitous insult. It figures.
Never mind that GUE's claim of being "one with the earth" and being focused on conservation would seem to mandate that absent a quantifyable benefit one should not consume a non-renewable resource simply for grins and giggles.
