Mac Flowpath catback here and I had to remove the muffler section from the flowtubes. It could have just been how they are mounted, but I did not have enough room to get to the bolt.
Otherwise, the install isn't bad... didn't have any problem with the bolts coming out. If you are worried about the bolt being seized, spray some PB Blaster (or other penetrating lubricant) on the bolt a few days before you go to remove them.
However, biggest PITA was pressing the new bushings in the LCA's. Tip: jam a small screwdriver or punch between the bushing and its housing when you are pressing them in (do this AFTER they are greased). This will let the air out and allow the bushing to fully seat. Thankfully my buddy gave me that tip, it kept me from going insane.