I just spoke with Jason and the new design has 8" mufflers. They went and built a crapload of the 6" systems, ran out of muffler caps, and now they are back to making axlebacks with the 8" mufflers because of the resonance produced with the header. When they increased the muffler size, it helped tremendously with the highway cruise he said.
My order will be shipping out tomorrow or thursday!
Didn't get a chance to ask him about if all of the axlebacks are all off-set by default. I'm sure you can still choose that option. All I know is, from here on out, every axleback for the FR-S/BRZ will be 8" mufflers. They do a lot of customizing so I'm sure you could request smaller mufflers if you don't plan on a header, but he said the tone and sound of the exhaust is unchanged. It makes the drive much more pleasant at highway cruise speed in 6th driving about an hour to his laser cutter and back with the catless header, OP/DP, and the revised axleback with the 8" mufflers.