KingP wrote (apparently in opposition to having a "long hose" with an Air2 type system)
it should be remembered that the average recreational diver is not going to have a lot of experience with losing their reg under water, so having their primary removed suddenly and with little or no warning (which is more likely with a long hose configuration than with a standard recreational configuration) is much more likely to make a bad situation worse.
Remember, the OP has already decided that he will donate his primary regulator should that become an issue because he has opted for the Air2 combo-inflator. So your concern is irrelevant to the question asked.
According to my LDS owner, more than 50% of the OW rigs he sells use the Air2 type system so this IS an issue for many new OW divers. The only question that should be considered is "How long should the hose be on the primary" when you have the combo-inflator system.
And I believe the answer is: "Longer than a standard primary hose." For example, last night I worked with 3 OW students who were trying out their brand new BCs, Regs, Dry suits, 'Puters (side comment, I figured Dad had just dropped about $20K for all the gear!) and all were using the Air2 system -- and all had "standard length" hoses on their 2nd stages -- NOT "octo length" hoses! They all found that having "standard length" hoses was a true PITA and when they did the same exercise with me, using a 40" hose they found air sharing much easier (I also have an AirSource system on my pool BC).
Do they need a 7 or 5 foot hose? No, although they might find the 5 footer useful after they gain some experience. Did they find the 26 inch hose useful? NO WAY!
Since this IS the regulator they donate, they really do need a "longer" hose than the norm and I believe the 36" hose (which I understand is a standard Octo length, although please feel free to correct me) works well but I prefer the slightly larger 40 inch hose for the routing.
So all remember, the OP, and those who use this system, DO NEED longer hoses than "standard" but how long, why it really depends on how much experience they acrue.
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BTW, TeamC, why do you say my hands would be tied up if I had a long hose provided to a panicked diver? Even with a total Hog rig/7 foot hose, I'd just hand off my primary, pick up my secondary and then have both hands free to calm/fend off (as the case may be) the diver. I ain't throwing the reg at him, I'm handing it off and so I can then grab him with my right hand if required. I can also hold him at arm's length if necessary which I may well NOT be able to do with the shorter "standard" Octo hose. I see LOTS of downsides to the short hose and none to the long(er) hose whether I'm a newbie or an experience technical diver.
BTW, I learned this lesson very early on when trying to do an airshare with my buddy using the short hose and the AirSource. We were so close neither of us could even kick to go up!