There has been a lot of speculation about the waterproof leather option, below is a link to the company that makes it. There was also speculation about it being plastic, let me assure you it is not if anything it has more of a slightly waxy feel to it. It seems to be very high quality stuff.
I guess if there are just 2 i would drill them both... The trick I doing it so "She Who must be..." does not know i did it! She is very anti me messing with the car. It does only have 350 miles on it!
kirkusblog.com 2016 M3W John A Prestwich Special 1952 Ford 8N 1968 Honda CL175,and 2018 Ural Retro
The rear baffle already has holes in it. I took it out with a hole saw first, beacuse it was easy to reach. Much nicer exhaust sound and a marked improvement on pinking.
The front one demands two extensions on the drill (= one more) and then it all starts to wobble. Approach from the front. It has no holes in it at all, the fumes go "around" it, so to speak. As a precaution against too much noise I have drilled four 9 mm holes in the front baffle and I am still evaluating. More, throatier exhaust rumble and the manifolds no longer glow red. Almost no pinking. Not sure I need to use the hole saw and there is room for at least four more 9 mm holes.
Oh, a tip for you: It takes forever to get the bit to bite into the stainless, but using an impact drill made it a doddle. It took seconds to drill a hole, in stead of several minutes.
Impact drill is a good idea, never thought of it. I sharpened the end of a long rod and center punched the front one first and then the hole saw didn't wobble.