^^^^
I've seen some of the Halcyon ones have an oral inflate & that you can also use your LP hose. Are there big advantages to this to say using your reg. The problem I can see with using your reg is if it gets tangled, in the SMB then away you go. Is this also a potential problem if you use your LP hose?
In cold water, it's really nice to be able to inflate your SMB with exhaust from your reg, since it keeps the inside of your reg dry, and cuts way down on the chances of having a free-flow and keeps your reg away from the bag and the line.
The tech @ Atomic mentioned that flooding your second stage then dumping a bunch of air out of it in very cold water drastically increases the chances of a free-flow, since the second stage doesn't have the same thermal protection as the sealed first stage. I took his advice, since I had a very nasty free-flow in very cold water, by inflating using my second stage.
OTOH, I've never been able to use the "exhaust" method and hang on to my Carter (same one you have) long enough get a decent amount of air into it, since even a 1/3 fill at depth is still 25 lbs of lift, which really starts to drag me up.
You can certainly inflate it with second stage, which will give you a nice fill in a hurry, however that leaves you with the possibility of a free-flow or entanglement and a
very rapid ascent.
In warm water, the method shown on the 5thd video works nicely. I thought it was s around here somewhere, but doesn't seem to show up on the search. In cold water, the best I've come up with is a safe but partial fill.
So far nobody on the surface has insulted me about my short tube
I have friends who use a "blower" attachment on a drysuit hose. It's decidely non-dir, and also has a pretty low flow rate compared to a second stage, so I'm not sure if that would get you anything. On the positive side, if you freeze it open, it's easy to unplug
I'll be watching to see if anybody has a better answer, since I'm not really happy with the current situation.
Terry
PS. sorry, I didn't even answer the question.
I carry a red and a yellow 75 lb Carter.