vector1, certainly one way to go although not as user friendly as the PVC Mock-Up Kit offered by these other guys
http://stainless.eclipticcms.com/customheaders
What I'm looking into now is corrective measures for a "too short" primary pipe length. What! No, I don't have that problem - just turning over more rocks. I think I can safely say "exhaust system engineering" is a lot like RF - freak'in BLACK MAGIC. Well, I'm an RF guy and I see some interesting parallels with exhaust systems and RF signal paths. (Yes Richard, I'm thinking WAY outside the box now). Being the savvy EE that I am, on more than one occasion electronic packaging has introduced unwanted VSWR to RF circuits (impedance mismatch - components in too close proximity to each other). In those instances, by screwing around with the circuit path downstream you can sometimes tune out the VSWR mismatch and get the throughput you want. So I'm looking at what corrective measures are out there with 4-1 collector designs, muffler lengths/diameters, and even primary ID tweaking to bring that mismatched exhaust system back in. Hey, it's all fun.
Looking forward to ...
RH lesson #318 - "Thinking outside the box, more often a poison than a remedy"