If you want to keep the 2 pipes I'm not quite sure why you'd want to reroute through 1 and have the other as a dummy. Wouldn't it be easier just to get a set of Roadster TORS or Staintunes? Or get both sides modded. Maybe Nev (or someone else) can shed some light on whether there's any particular advantage of 3 into 1 v 3 into 2, other things being equal.
By the way, welcome from Canberra.
Good to have you join us. You obviously are looking to "improve" on stock; you'll find us both interested and helpful - and maybe even interesting.