Disagree. I have a pair of 2.5" put thru mine. Stock brace is in place. No big problem for local exhaust shop. It's TIGHT, but nothing touches or bumps anything thru there.

Hard to take pics with car on ground, but you get the idea. First is the front of the brace where shop put in a 2.5" crossover pipe as the pipes bend inward to enter the brace. 2nd photo I kinda missed the shot, but it's the pipes exiting the brace at the rear.

$267.50 parts/labor/tax included out the door. Included crossover, basic single unfinished turn-down behind each quarter in the usual F-bird exit location, and a pair of Thrush mufflers (cheap Flowmaster knockoffs). They just fabbed it all up on the fly by eye-balling it outta their straight 2.5" stock.

Shop is called Mufflers and More, Noblesville, IN. I highly recommend them for budget, functional, decent quality exhaust systems and/or other mechanical repairs. Concourse work it is not. But they provide what I call the rare combo of "cheap and good."

Didn't even have to get my hands dirty for that little project...sat in a waiting room for about 2 hours. Since I couldn't even buy the parts for the installed price I figured I had nothing to lose...