Yeah, I'm debating what to do with flex, etc. I'm not 100% happy with the quality of the work of the place I went either. I'll give him a shot to fix it, but then I'll be headed elsewhere. The welds and such are fine, but the fitment, checking, measuring was a little haphazard. I was having to fix/adjust things as he worked on it. :/
I would still investigate the MF Tru-X mufflers. They are marketed as a "resonated X-pipe". You can see straight through them like an X-pipe.
I'll see if I can find the video to share, but a local SS owner had Kooks LTs, Kooks catless mid pipe, to stock 2015 SS mufflers, and it was crazy loud with his BTR stage 3 cam. He added a MF muffler to the kooks midpipe and tamed it down nicely. So yeah, he had 2 x-pipes, but apparently there is a bit of info out there supporting the benefit (or at least not loss) of having 2 x-pipes.
2009 PBM GT
Under the Knife Again
Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
Breyton GTS-AV Wheels, 6k HIDs, Holden Steering Wheel and Paddle Shifters, Eibach Springs, 35% Tint
Tuned by Day Tuning