Solution to catalytic converter theft:

Get a piece of hardened or wear plate steel (manganese alloy) from a metal fabrication shop, maybe 1/4" (0.75cm) by 1" (2.5cm) about 36 - 42" (90 - 110cm) long (long enough to follow the pipe where it passes above the cross frame. Have the muffler shop MIG weld this bar to the exhaust pipe in front of and behind the cat. converter.
Manganese alloyed steel cannot be cut with any pipe cutter or saw, it can only be cut with a cutting torch or abrassive cutoff wheel. Using the later to cut throught the wear plate steel would take 5 - 10 minutes and create a lot of sparks and noise. Most thieves need to be in & out in less than 3 minutes without creating any sound.