Relax!

There's no rule that says you have to get this perfect the first try. If you think you'll want straight pipes, build the system that way. If it's too loud or raspy, add mufflers. Its just a matter of cutting a section of pipe out and installing the muffler in its place. Or you could use muffler tips. I wonder what it would sound like with a pair of ricer fart pipes on the end of a straight exhaust.

I'm running a pair of 22" Smithys on my 55 235. I like the way it sounds.

regards,
Leon