Not sure of the sound you refer to...maybe the crackling/ popping when you back off? I think that is a combination of smaller diameter tailpipes & slightly rich mixture. Others may have different thoughts on this.
You're going to make your own mufflers? Any reason you don't just buy a set? Just curious...
Have you "heard" of Porter Mufflers?
http://portermufflers.com/products/p...inal-mufflers/
They were the original steel packs from the 1930's. They went out of business, but were resurrected a few years ago. Their construction is about what you described.
I hope that helps.
Bill