Don't mess with trying to rig something up. All you'll end up doing is wasting money because it won't work out quite right and you'll have to spend more money to get something else.
The best comfort and utility for the money I've found for a pack is this one from Flurry.
It comes with all of the attachments that you see in the picture so you can set it up any way you want. Run 1 pod, or 2 or 5 and angle them how you want to as well. You can use the tank holder if you want or leave it off. it has a mask strap too so you can hang your mask when not playing.
They have a free shipping code as well for the packs right now PACKSHIP That makes that harness a steal.