Ummm... I can't even find this style plate on the Miller website, which is perhaps why it required drilling to install. The correct Miller Cat Shield is the 2016 - 2021 Gen 4 shield, I got one and it is a no-drill operation. The toughest part is raising the car enough to get enough clearance... so a fat old geezer like myself is better off having a place with a lift do the install. The correct plate with holes already aligned with existing rail bolts:
Arrrgh... that's why it was a hassle to install: it is NOT a Miller Cat shield!!! Check the video and you'll find it is a CCM brand shield (VS MillerCat):
Also the CCM brand is aluminum whereas the one we are using is stainless steel, hence the price difference. Cat Security™ 2016-2021 Prius
If it was my car, I'd install the CCM version or its knock off equivalent using the Miller Cat method with the rivet nuts. To make the screws really hard to remove, I'd fill the heads with putty or sealant.
I suspect Prius catalyst thieves are using Sawzalls capable of cutting aluminum plates like a hot knife going through butter, hence my preference for a much more robust stainless steel shield. Perhaps a truly determined cat-napper could still prevail, but ya' may as well make 'em work for it (on the hope they'll move on to easier prey).
That thin stainless steel is easily cut with a battery powered angle grinder and ab abrasive cutoff disc. The edge of the same disc will easily grind off and fastener. Why bother with a Sawzall bit to cit off the round exhaust pipe? The shield is a deterrent. Thieves will most likely go elsewhere.
I understand grinders don't work well on aluminum because the aluminum loads up the wheel. That's true on a bench grinder but don't know if true using a cutoff wheel.
So you need a different disc to cut steel vs aluminum. I doubt thieves will take the time to change discs. Or carry two cutoff tools. Discs are slow so I think a Sawsall is the tool of choice.
Not slow at all on thin metal like exhaust pipes. Also, just angle the edge of the disc on any rivet or bolt, and it easily grinds off. The aluminum cut off disc will also readily cut stainless steel.