Having a 3ft hose for the octo, this octo when mounted on the left is perfectly suited for your buddy, and the hose is also more than long enough for you to use your own octo if needed.
Having your regular primary mounted on the right, and your octo mounted on the left also offers your buddy an "always grab something useful" oppertunity when being in a panic situation regardless of he's was swimming on your left or right... if he's on the right and it is an "extremely urgent" OOA such that there is no time for signalling an OOA and waiting a few seconds for getting the octo he's free to grab your own primary and you switch to your octo (with in this case the hose "bended" in S but for yourself it is still more than long enough) and after 10-30sec when he's getting air, and getting calm again, you might convince him to switch regs to a more comfortable situation, i.c. you get your primary back and he gets your octo... and if he was swimming on your left, he clearly sees the bright yellow LP-hose of your octo and he can easily grab it himself. Especially in case of panic it is of vital importance to offer as many solutions/possibilities as possible and having both your primary and octo at the right side simply reduces the possibilities without any good reason at all!