Id go a step further and not breath any tank down at once. If you swap regs every 10 bar you will always have around the same amount of gas in all your tanks and your turn around point is easy to work out.
As for the streamlining them have you ever tried sidemounts? Dive Rite do a kit for the Transpac 2 system that works great. Holds everything nice and close but aslo out of the way. There are a few others that make sidemounted BCs if you look around. Armadillo is another maker.
Matt