A lot can be done in properly mounting and TIGHTENING the exhaust system in place to yield at least 1/4" more clearance, if you are methodical.
I work from the head to the tail in setting them up "finger tight", then another pass front-to-back checking everything like shifter (toe) contact, brake pedal range, pipes, etc., then one last pass back-to-front to allow max clearance at the pipes, while keeping symmetry as close as possible for aesthetics.
I have, at times, inserted some shimming where required to ensure clearance, while final tightening.