If you hollow the cat, you'll lose a lot of heat and pressure that drives the turbo. You can probably get a replacement part form www.pgauto.com.

While waiting, have a muffler shop weld up a pipe with flanges similar to the trap. Maybe you can cut the flanges off the trap and join them with some 2.5" pipe.

Is Nodalos still in business?

Sixto
... stay tuned