So I understand the idea is to go for a PE sound which I have never heard but something comes to mind.
In my old mustang world you had SLP loudmouth series mufflers(resonators)
The louder version was completely flow through
see here for pic
Then you had the quieter more refined loudmouth 2 version
See here for pic
So I wonder if what the speculations are you leave the one perforated pipe,then cut out the little catalytic looking thing and add another perforated pipe and then pack the rest of the open space of the muffler with packing?