Back to questioning my exhaust setup, since there is no way to fit dual 3" over the axle, a single 4" is the future. With the massive Flopro taking up so much space I don't think there would be room for a merge pipe after the muffler, and I don't think the available off-the-shelf merge pipes would fit the odd offset of the Flopro outlets (See pic 1). The search for a dual 3" inlet single 4" outlet muffler led me to the Gibson 788050S (link/pic below), its 8" round, 24" body, and 30"total where the Flopro is 12x9 and same body length. My main concern would be that since it has significantly less internal volume its ability to reduce drone would be reduced, maybe the 4" outlet would be quieter than the dual 3"?
The possibility of adding a 4" resonator after the axle is a good possibility, or a pair of 3" before the muffler still possible just more difficult.
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https://www.amazon.com/Gibson-Performance-Exhaust-788050S-Stainless/dp/B008CLO6YU)