If only the "strap em (vertically) to the LHS" divers could learn some streamlining from the Sidemount diversDo you have any SideMount experience? I "self taught" SideMount with the instructional videos from Sidemounting.com and a good amount of free-time. It can be somewhat challenging, frustrating, and finicky.
That said, I have done sidemount (just side-mount, with no back tank), by adding bungies under the arms, adjusting the d-rings, and using some bungies to prevent the wing from turning into a parachute. Since you have the backmount tank, you wouldn't need to worry about the last part about the wing.
The other thing to consider with your setup is balancing your bouyancy left/right. With aluminum tanks, it's not too bad. About 1.5 to 2lbs on the opposite side should do the trick. With steel, it's a pain to get right, but you'll want about 4-5lbs.
Aside from sidemount, you could do the basic mimic technical divers, when the bring extra cylinders. I'm not a technical-diver, so I can't answer questions, but basically this:
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But now we've mentioned sidemount, the name that shouldn't be mentioned, the OP would be in a massively better position when travelling. Sling on a couple of ali80's and there's loads of gas, with loads of streamlining, with loads of stability. So much nicer than backmount.
Sidemount does require a dedicated harness & wing -- the XDeep Stealth Tec is great, along with many others. It takes a while to get it configured correctly which can be massively helped by seeking a good sidemount instructor. Once sorted, it's so much easier.