Replacing single rear tire, must I shave?

[prochobo]

Got a chunk of my sidewall blown off on one of my rears. My other tire is good with plenty of tread left, but I was wondering if there was any OEM recommendation as to how much the rear tires' tread can differ by.

E.g. from Tire Rack:

Here are recommendations from some of the manufactures that Tire Rack currently serves for matching the tires used on their four-wheel drive and all-wheel drive vehicles. Additional recommendations from other Original Equipment Vehicle Manufacturers is pending.

Audi As published in their vehicle owner's manual, "rolling radius of all 4 tires must remain the same" or within 4/32-inch of each other in remaining tread depth.
Porsche Cayenne within 30% of the other tire on the same axle's remaining treadwear.
Subaru Within 1/4-inch of tire circumference or about 2/32-inch of each other in remaining tread depth.