Well..
Ok, so I am trying to start a touch of trouble.
First trouble: You don't need formal sidemount training to dive sidemount in any location. While training or mentoring, formal or not is an asset it is not an necessity. Bad training is worse than no training.
Second trouble: A long hose is a waste of time on sidemount unless you are diving a mixed team. Should you use one, there are as many ways to stow it as there are sidemount divers. Only one of these methods can you actually deploy it "as fast" as someone on backmount. Diving with your "hands at your chest" the whole time is bunk. You are not, and you know it. If you aren't running a reel, your pulling and gliding or taking survey notes or something. Now try it in dry gloves without you're hand on the clip already. Now do it with frozen fingers. Now try it with a seized clip. You also have to be aware of which reg you're on so you know what to donate. Making choices during the only true emergency at depth is not my idea of ideal. If there is any skill that needs to be a hard wired reaction, it's this one.
I will detail what I view are the "best" ways to run a long hose on sidemount below.
Third trouble: It is clear you are very enthusiastic and its great to see you sharing. It is also clear you are new to sidemount (I hope). There are some things about your rig that would need some looking at if you decide to go small. In your video of the ballroom you have difficulty getting though a backmount area without bumping and grinding. If you would like to pursue that line of thought, PM me you're email address.
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Ok, done stirring the trouble pot.
How I would route a long hose on sidemount:
Ideal: Run two. One bungeed to each tank. You have just recovered the "donate from mouth ease of backmount. All your hard training there is now instantly accessible and your backmount buddies don't need to know or do anything differently. In a silt out, they just take from your mouth as always. Due to the required hose wrapping and what not, this is only appropriate if you aren't going to be removing gear. But, if you're with a backmount team that shouldn't be an issue. This is the only way I can see having a donation as easily and quickly as a backmount setup.
Compromise: Set up your rig for sidemount with short hoses. Pick a tank, add a second second stage (or an h-valve and second first). Bungee that to the tank. Always donate from the tank. You retain the ability to go small and you have one response. This can get dangerous stupid if you have deco bottles on, so put it on your right side and don't carry stages there. No clips, just grab the reg and pull.. but its going to be slower and less 100% sure than donate from mouth.