I have to say.. lifting before T6 is no fun but it is plausible and a worthwhile strategy.
The MRLS sound check system isn't a perfect science. I've seen cars get meatballed incorrectly. For example, if there is a cluster of 3... they have no idea which car is the louder one realistically speaking. If you're the unlucky guy who got flagged because the guy near you was louder, there is no hope for appeal. With most organizers i'm familiar with, once you're meatballed twice, you're out for the rest of the day. Also the doppler effect can get tricky on any given day, especially when comparing a hot day vs. a foggy cool morning. Sound travels differently.
My track exhaust config is virtually a slightly muffled, no cat, open header system. It's loud. However, my Laguna Seca package includes HF cats and these. I'm curious if I can be below 92dB on the first pass. If I still fail, I will close the bypass valves. It robs some power but is quieter even still.
Daniel - perhaps you can look into these. If you choke off all 4 tips on your v5.1, you'll still be flowing the same volume technically as the main piping. Mine sounds anemic with these things on though. lol