Just occurred to me but have you thought of installing a “reducer” similar to the RPi silencers? I think the tips on the Powerloops are 80mm but they’re not perfectly circular. On the shortest diameter it’s probably close to 70mm, so something like this may work:
http://www.everyexhaustpart.com/cart...expander.htmlQ
You basically need to drill a small hole underneath and secure the reducer with a nut and bolt:
https://www.raceprecision.com/product/RPI-RP-023.html