And to add to that. Before buying the reg make sure your instructor will allow you to use it in that configuration.
And that he or she even knows how to do it. I just had an exchange with another member whose instructor for a family member said a long hose with bungee was not acceptable.
He wrongly stated that the octo needed to be on a 40-48 inch hose, yellow in color, and attached at the right hip by standards(he did not specify if this was agency or shop standards). If he meant agency this was BS as I do have the current standards for that class. But it may be his shop's standard which if so, oh well.
I think making new divers use gear they have already clearly said they will not be using after the class is shortsighted and potentially dangerous. I would have no problem teaching someone who showed up with a double hose that had an octo and SPG attached with an LP inflator hose to a horsecollar and a weight belt with rocks in the pockets. It meets the stanadards.
I would hate to see the OP show up for class with a set up and be told he could not use it. It would be bull crap but it could happen.