Many MFRs will state "does not fit the convertible" (including Borla) when they can be adjusted by a smart installer to fit without rattling against the rear X brace (albeit with tight clearances).
There are a few success story posts on this forum:
https://www.camaro6.com/forums/showthread.php?t=590702
https://www.camaro6.com/forums/showthread.php?t=605642
https://www.camaro6.com/forums/showthread.php?t=492590
https://www.camaro6.com/forums/showthread.php?t=521147